Strange virtualbox behavior

[Temtaime]

Hi guys!
When i tried save my virtual box machine i got following error: VBoxManage.exe: error: Machine in invalid state 4 -- aborted

And machine's log contains strange lines:
18:50:51.686390 AHCI#0P0: Cancelled task 0
18:50:55.606280 AHCI#0: Port 0 reset
18:50:57.501928 AHCI#0P0: Write request was active for 36 seconds
18:50:57.758013 AHCI#0P0: Canceled write at offset 2314690560 (4096 bytes left) returned rc=VINF_SUCCESS
19:54:41.616854 AHCI#0P0: Cancelled task 0
19:54:51.125676 AHCI#0P0: Write request was active for 40 seconds
19:54:51.513800 AHCI#0: Port 0 reset
19:54:51.525474 AHCI#0P0: Canceled write at offset 12513218560 (36864 bytes left) returned rc=VINF_SUCCESS
24:31:35.631725 AHCI#0P0: Cancelled task 0
24:31:37.299519 AHCI#0P0: Write request was active for 32 seconds
24:31:37.299548 AHCI#0P0: Canceled write at offset 12554760192 (8192 bytes left) returned rc=VINF_SUCCESS
24:31:37.299574 AHCI#0: Port 0 reset
25:29:49.611722 AHCI#0P0: Cancelled task 1
25:30:02.733669 AHCI#0P0: Write request was active for 40 seconds
25:30:02.733686 AHCI#0P0: Canceled write at offset 2112880640 (180224 bytes left) returned rc=VINF_SUCCESS
25:30:02.733772
25:30:02.733773 !!Assertion Failed!!
25:30:02.733773 Expression: !ASMAtomicReadU32(&pAhciPort->cTasksActive)
25:30:02.733774 Location : D:\tinderbox\win-4.3\src\VBox\Devices\Storage\DevAHCI.cpp(5594) bool __cdecl ahciCancelActiveTasks(struct AHCIPort *)

What it can be? Thanks.