Since 1.6 was introduce there is bug which cause crash of vbox on linux if host system went in to standby mode. After resume:
Aug 9 11:06:10 opahapaka kernel: invalid opcode: 0000 [#3] PREEMPT SMP
Aug 9 11:06:10 opahapaka kernel: Modules linked in: vboxdrv tun hci_usb iwl4965 snd_pcm_oss snd_mixer_oss snd_hda_intel
snd_usb_audio snd_pcm snd_timer snd_usb_lib snd_rawmidi snd_seq_device snd_hwdep snd soundcore snd_page_alloc mmc_block
cdc_acm usbhid usbkbd xfs usb_storage rfcomm l2cap uinput bluetooth arc4 ecb crypto_blkcipher cryptomgr crypto_algapi
nvidia(P) nvidiafb iwlcore pcmcia fb_ddc i2c_algo_bit sdhci i2c_i801 vgastate pcspkr uhci_hcd ohci1394 mac80211
ehci_hcd psmouse mmc_core ieee1394 yenta_socket rsrc_nonstatic pcmcia_core usbcore e1000 i2c_core cfg80211 [last unloaded: vboxdrv]
Aug 9 11:06:10 opahapaka kernel:
Aug 9 11:06:10 opahapaka kernel: Pid: 16497, comm: VirtualBox Tainted: P R D (2.6.25.10 #1)
Aug 9 11:06:10 opahapaka kernel: EIP: 0060:[<f8d3146a>] EFLAGS: 00210046 CPU: 0
Aug 9 11:06:10 opahapaka kernel: EIP is at 0xf8d3146a
Aug 9 11:06:10 opahapaka kernel: EAX: 00000000 EBX: 00000000 ECX: 2d06f000 EDX: 00000000
Aug 9 11:06:10 opahapaka kernel: ESI: 00000000 EDI: f8d85000 EBP: ecdf7ed0 ESP: ecdf7ebc
Aug 9 11:06:10 opahapaka kernel: DS: 007b ES: 007b FS: 00d8 GS: 0033 SS: 0068
Aug 9 11:06:10 opahapaka kernel: Process VirtualBox (pid: 16497, ti=ecdf6000 task=f0fbe570 task.ti=ecdf6000)
Aug 9 11:06:10 opahapaka kernel: Stack: 2d06f000 00000000 00000000 f8d85000 00200246 ecdf7f00 f8d2b3ca f8d85000
Aug 9 11:06:10 opahapaka kernel: f8d7bce0 c0285609 f12a4190 f8d17fa8 f8d85000 00000006 f8d859c0 f8d15110
Aug 9 11:06:10 opahapaka kernel: f8d85000 ecdf7f20 f8d32ebb f8d85000 00200282 f8d188ee f8d15110 f2a28800
Aug 9 11:06:10 opahapaka kernel: Call Trace:
Aug 9 11:06:10 opahapaka kernel: [<c0285609>] redo_fd_request+0x904/0xdb8
Aug 9 11:06:10 opahapaka kernel: [<f8d17fa8>] supdrvIOCtl+0xe6e/0x12a2 [vboxdrv]
Aug 9 11:06:10 opahapaka kernel: [<f8d15110>] VBoxDrvLinuxIOCtl+0x0/0x15f [vboxdrv]
Aug 9 11:06:10 opahapaka kernel: [<f8d188ee>] rtMemAlloc+0x29/0x47 [vboxdrv]
Aug 9 11:06:10 opahapaka kernel: [<f8d15110>] VBoxDrvLinuxIOCtl+0x0/0x15f [vboxdrv]
Aug 9 11:06:10 opahapaka kernel: [<f8d156fb>] supdrvIOCtlFast+0x3f/0x4a [vboxdrv]
Aug 9 11:06:10 opahapaka kernel: [<f8d1513d>] VBoxDrvLinuxIOCtl+0x2d/0x15f [vboxdrv]
Aug 9 11:06:10 opahapaka kernel: [<f8d15110>] VBoxDrvLinuxIOCtl+0x0/0x15f [vboxdrv]
Aug 9 11:06:10 opahapaka kernel: [<c01697f8>] vfs_ioctl+0x1c/0x5f
Aug 9 11:06:10 opahapaka kernel: [<c0169a6a>] do_vfs_ioctl+0x22f/0x241
Aug 9 11:06:10 opahapaka kernel: [<c0131575>] do_gettimeofday+0xf/0x29
Aug 9 11:06:10 opahapaka kernel: [<c0169aa8>] sys_ioctl+0x2c/0x44
Aug 9 11:06:10 opahapaka kernel: [<c0103c76>] sysenter_past_esp+0x5f/0x85
Aug 9 11:06:10 opahapaka kernel: =======================
Aug 9 11:06:10 opahapaka kernel: Code: 75 11 89 f0 8b 1c 24 8b 74 24 04 8b 7c 24 08 89 ec 5d c3 8b 9f 48 e0 00 00
31 f6 8b 8f 44 e0 00 00 89 da 89 c8 89 d0 31 d2 50 51 <0f> c7 34 24 73 05 be 5f f0 ff ff 83 c4 08 85 f6 78 c5 31 f6 c6
Aug 9 11:06:10 opahapaka kernel: EIP: [<f8d3146a>] 0xf8d3146a SS:ESP 0068:ecdf7ebc
Aug 9 11:06:10 opahapaka kernel: ---[ end trace 68831b3a78f1d3e7 ]---
Aug 9 11:06:10 opahapaka kernel: done.
In 1.5.6 it is stable.