Similar thing on my real hardware, random, at shutdown:

fixme:(base\system\winlogon\sas.c:651) FIXME: Call SMSS API #1
(hal\halx86\generic\bios.c:83) HAL: An invalid V86 opcode was encountered at address c000:989b
Entered debugger on embedded INT3 at 0x0008:0x808db5fe.bt
Eip:
<ntoskrnl.exe:db5ff (lib\rtl\i386\debug_asm.S:33 (DbgBreakPoint@0))>
Frames:
<hal.dll:36e6 (hal/halx86/generic/bios.c:197 (@HalpDispatchV86Opcode@4))>
<hal.dll:373f (hal/halx86/generic/bios.c:230 (@HalpTrap0DHandler@4))>
<00000001>
<00000000>