virtualbox crash after random time

i am using a windows 7 virtual machine on ubuntu 14.04 and my virtualbox version is 15.04. When I open virtual machine, after some time it gets aborted. And then it always aborts during the opening animation. I can only open it again if I restart ubuntu. Here are the last logs of the virtual machine :

00:00:00.640818 VMEmt: Halt method global1 (5)
00:00:00.640915 VMEmt: HaltedGlobal1 config: cNsSpinBlockThresholdCfg=2000
00:00:00.641132 Changing the VM state from 'CREATING' to 'CREATED'
00:00:00.645234 Changing the VM state from 'CREATED' to 'POWERING_ON'
00:00:00.645412 AIOMgr: Endpoints without assigned bandwidth groups:
00:00:00.645423 AIOMgr: /home/saim/VirtualBox VMs/windows7-64/virtualstorage.vdi
00:00:00.645427 AIOMgr: /usr/share/virtualbox/VBoxGuestAdditions.iso
00:00:00.645430 AIOMgr: /home/saim/VirtualBox VMs/64BitWindows/64BitWindows.vdi
00:00:00.645511 Changing the VM state from 'POWERING_ON' to 'RUNNING'
00:00:00.645519 Console: Machine state changed to 'Running'
00:00:00.651192 VMMDev: Guest Log: BIOS: VirtualBox 5.0.14
00:00:00.652413 PIT: mode=2 count=0x10000 (65536) - 18.20 Hz (ch=0)
00:00:00.666092 Display::handleDisplayResize: uScreenId=0 pvVRAM=0000000000000000 w=720 h=400 bpp=0 cbLine=0x0 flags=0x1
00:00:00.678808 AHCI#0: Reset the HBA
00:00:00.678854 AHCI#0: Port 0 reset
00:00:00.679208 VMMDev: Guest Log: BIOS: AHCI 0-P#0: PCHS=16383/16/63 LCHS=1024/255/63 0x00000000061a8000 sectors
00:00:00.679249 AHCI#0: Port 1 reset
00:00:00.679641 AHCI#0: Port 2 reset
00:00:00.680035 VMMDev: Guest Log: BIOS: AHCI 2-P#2: PCHS=16383/16/63 LCHS=1024/255/63 0x000000000a000000 sectors
00:00:00.680558 PIT: mode=2 count=0x48d3 (18643) - 64.00 Hz (ch=0)
00:00:00.686129 Display::handleDisplayResize: uScreenId=0 pvVRAM=00007fe442500000 w=640 h=480 bpp=32 cbLine=0xA00 flags=0x1
00:00:03.165998 PIT: mode=2 count=0x10000 (65536) - 18.20 Hz (ch=0)
00:00:03.166144 VMMDev: Guest Log: BIOS: Boot : bseqnr=1, bootseq=0231
00:00:03.166253 VMMDev: Guest Log: BIOS: Boot from Floppy 0 failed
00:00:03.166374 VMMDev: Guest Log: BIOS: Boot : bseqnr=2, bootseq=0023
00:00:03.169154 Display::handleDisplayResize: uScreenId=0 pvVRAM=0000000000000000 w=720 h=400 bpp=0 cbLine=0x0 flags=0x1
00:00:03.174995 VMMDev: Guest Log: BIOS: CDROM boot failure code : 0004
00:00:03.175091 VMMDev: Guest Log: BIOS: Boot from CD-ROM failed
00:00:03.175208 VMMDev: Guest Log: BIOS: Boot : bseqnr=3, bootseq=0002
00:00:03.202356 VMMDev: Guest Log: BIOS: Booting from Hard Disk...
00:00:03.410047 Display::handleDisplayResize: uScreenId=0 pvVRAM=00007fe442500000 w=1024 h=768 bpp=24 cbLine=0xC00 flags=0x1
00:00:05.761057 Display::handleDisplayResize: uScreenId=0 pvVRAM=00007fe442500000 w=1024 h=768 bpp=24 cbLine=0xC00 flags=0x1
00:00:05.803725 VMMDev: SetVideoModeHint: Got a video mode hint (1920x992x24)@(0x0),(1;0) at 0
00:00:09.724482 RTC: period=0x200 (512) 64 Hz
00:00:09.926190 GIM: HyperV: Guest OS reported ID 0x1040601011db1
00:00:09.926211 GIM: HyperV: Open-source=false Vendor=0x1 OS=0x4 (Windows NT or derivative) Major=6 Minor=1 ServicePack=1 Build=7601
00:00:09.926267 GIM: HyperV: Enabled TSC page at 0x000000003fffe000 - u64TscScale=0xc12ff400000000 u64TscKHz=0x33c363 (3 392 355) Seq=1
00:00:09.926315 TM: Switching TSC mode from 'VirtTscEmulated' to 'RealTscOffset'
00:00:11.484414 AHCI#0: Reset the HBA
00:00:11.543132 VMMDev: Guest Log: VBoxGuest: Windows version 6.1, build 7601
00:00:11.565450 VMMDev: Guest Additions information report: Version 5.0.14 r105127 '5.0.14'
00:00:11.565534 VMMDev: Guest Additions information report: Interface = 0x00010004 osType = 0x00037100 (Windows 7, 64-bit)
00:00:11.576510 VMMDev: Guest Additions capability report: (0x0 -> 0x0) seamless: no, hostWindowMapping: no, graphics: no
00:00:11.578607 VMMDev: Guest reported fixed hypervisor window at 00008400000 LB 0x3400000 (rc=VINF_SUCCESS)
00:00:11.578640 VMMDev: vmmDevReqHandler_HeartbeatConfigure: No change (fHeartbeatActive=false).
00:00:11.578670 VMMDev: Heartbeat flatline timer set to trigger after 4 000 000 000 ns
00:00:15.543493 AIOMgr: Flush failed with VERR_INVALID_PARAMETER, disabling async flushes
00:00:15.966636 VMMDev: Guest Log: VBoxMP::DriverEntry: VBox XPDM Driver for Windows version 5.0.14r105127, 64 bit; Built Jan 19 2016 16:43:24
00:00:17.735541 VMMDev: Guest Log: VBoxMP::VBoxDrvFindAdapter: using HGSMI
00:00:17.888554 HDA: Reset
00:00:17.912842 HDA: Reset
00:00:17.953932 OHCI: Software reset
00:00:17.954068 OHCI: USB Reset
00:00:18.021678 OHCI: USB Operational
00:00:19.267465 OHCI#0: Lagging too far behind, not trying to catch up anymore. Expect glitches with USB devices
00:00:20.599253 Display::handleDisplayResize: uScreenId=0 pvVRAM=00007fe442500000 w=1920 h=992 bpp=24 cbLine=0x1680 flags=0x1
00:00:20.831085 VMMDev: Guest Log: VBoxDisp[0]: VBVA enabled
00:00:20.831120 VBVA: InfoScreen: [0] @0,0 1920x992, line 0x1680, BPP 24, flags 0x1
00:00:20.831127 Display::handleDisplayResize: uScreenId=0 pvVRAM=00007fe442500000 w=1920 h=992 bpp=24 cbLine=0x1680 flags=0x1
00:00:29.475454 RTC: period=0x20 (32) 1024 Hz
00:00:29.497559 RTC: period=0x100 (256) 128 Hz
00:00:34.583877 RTC: period=0x200 (512) 64 Hz
00:00:34.600434 RTC: period=0x20 (32) 1024 Hz
00:00:34.615166 RTC: period=0x200 (512) 64 Hz
00:00:48.028415 Starting host clipboard service
00:00:48.028455 ClipConstructX11: X11 DISPLAY variable not set -- disabling shared clipboard
00:00:49.131437 RTC: period=0x20 (32) 1024 Hz
00:00:49.154033 RTC: period=0x100 (256) 128 Hz
00:00:49.598707 VMMDev: Guest Additions capability report: (0x0 -> 0x1) seamless: yes, hostWindowMapping: no, graphics: no
00:00:49.600084 VMMDev: Guest Additions capability report: (0x1 -> 0x5) seamless: yes, hostWindowMapping: no, graphics: yes
00:00:49.989853 RTC: period=0x200 (512) 64 Hz
00:00:58.734365 AIOMgr: Flush failed with VERR_INVALID_PARAMETER, disabling async flushes
00:01:00.115790 RTC: period=0x20 (32) 1024 Hz
00:01:00.146143 RTC: period=0x100 (256) 128 Hz
00:01:16.139185 RTC: period=0x20 (32) 1024 Hz
00:01:19.021395 RTC: period=0x100 (256) 128 Hz
00:01:19.116246 RTC: period=0x20 (32) 1024 Hz
00:01:19.146027 RTC: period=0x100 (256) 128 Hz
00:01:19.147019 RTC: period=0x20 (32) 1024 Hz
00:01:19.162007 RTC: period=0x100 (256) 128 Hz
00:01:19.178779 RTC: period=0x20 (32) 1024 Hz
00:01:30.677813 RTC: period=0x100 (256) 128 Hz
00:01:50.874018 RTC: period=0x20 (32) 1024 Hz
00:01:50.904339 RTC: period=0x100 (256) 128 Hz
00:01:55.139348 RTC: period=0x20 (32) 1024 Hz
00:01:55.169999 RTC: period=0x100 (256) 128 Hz
00:02:16.608283 RTC: period=0x20 (32) 1024 Hz
00:02:16.732244 RTC: period=0x100 (256) 128 Hz
00:02:16.780490 RTC: period=0x20 (32) 1024 Hz
00:02:16.927832 RTC: period=0x100 (256) 128 Hz
00:02:17.100864 RTC: period=0x20 (32) 1024 Hz
00:02:17.130883 RTC: period=0x100 (256) 128 Hz
00:02:17.944080 RTC: period=0x20 (32) 1024 Hz
00:02:17.974424 RTC: period=0x100 (256) 128 Hz
00:02:18.413352 RTC: period=0x20 (32) 1024 Hz
00:02:18.443517 RTC: period=0x100 (256) 128 Hz
00:02:22.117120 RTC: period=0x20 (32) 1024 Hz
00:02:22.146359 RTC: period=0x100 (256) 128 Hz
00:02:25.288096 RTC: period=0x20 (32) 1024 Hz
00:02:25.482420 RTC: period=0x100 (256) 128 Hz
00:02:25.845334 RTC: period=0x20 (32) 1024 Hz
00:02:25.880384 RTC: period=0x100 (256) 128 Hz
00:02:26.451828 RTC: period=0x20 (32) 1024 Hz
00:02:26.484247 RTC: period=0x100 (256) 128 Hz
00:02:26.670882 RTC: period=0x20 (32) 1024 Hz
00:02:26.746077 RTC: period=0x100 (256) 128 Hz
00:02:27.162727 RTC: period=0x20 (32) 1024 Hz
00:02:27.193518 RTC: period=0x100 (256) 128 Hz
00:02:27.278847 RTC: period=0x20 (32) 1024 Hz
00:02:27.326369 RTC: period=0x100 (256) 128 Hz
00:02:27.358192 RTC: period=0x20 (32) 1024 Hz
00:02:27.388601 RTC: period=0x100 (256) 128 Hz
00:02:29.623553 RTC: period=0x20 (32) 1024 Hz
00:02:29.693079 RTC: period=0x100 (256) 128 Hz
00:02:29.868003 RTC: period=0x20 (32) 1024 Hz
00:02:29.912245 RTC: period=0x100 (256) 128 Hz
00:02:37.709843 RTC: period=0x20 (32) 1024 Hz
00:02:37.740212 RTC: period=0x100 (256) 128 Hz
00:02:38.853847 RTC: period=0x20 (32) 1024 Hz
00:02:38.880924 RTC: period=0x100 (256) 128 Hz
00:02:39.858202 RTC: period=0x20 (32) 1024 Hz
00:02:39.960996 RTC: period=0x100 (256) 128 Hz
00:02:39.967450 RTC: period=0x20 (32) 1024 Hz
00:02:39.998079 RTC: period=0x100 (256) 128 Hz
00:02:42.334643 RTC: period=0x20 (32) 1024 Hz
00:02:42.381122 RTC: period=0x100 (256) 128 Hz
00:02:50.592825 RTC: period=0x20 (32) 1024 Hz

Thanks for help