Crash when test threads exceed 256

--threads 256 works fine, but ---threads 257 goes boom:

Unhandled exception at 0x0041a05c in omniscient.exe: 0xC0000005: Access violation writing location 0x00000000.

>	omniscient.exe!memcpy(unsigned char * dst=0x00000000, unsigned char * src=0x600e46d9, unsigned long count=3)  Line 372	Asm
 	omniscient.exe!xd3_decode_output_halfinst(_xd3_stream * stream=0x1545f8bc, _xd3_hinst * inst=0x1545fc4c)  Line 451	C++
 	omniscient.exe!xd3_decode_emit(_xd3_stream * stream=0x00000000)  Line 756 + 0x7 bytes	C++
 	omniscient.exe!xd3_decode_input(_xd3_stream * stream=)  Line 1178 + 0x7 bytes	C++
 	omniscient.exe!PatchFile(const std::basic_string<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t> > & inputPath="srcwads/doom_pocketpc.wad", const std::basic_string<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t> > & patchPath={...}, const std::basic_string<wchar_t,std::char_traits<wchar_t>,std::allocator<wchar_t> > & outputPath={...})  Line 105	C++
 	omniscient.exe!TestThreadFunc(void * lpParam=)  Line 135 + 0x49 bytes	C++
 	kernel32.dll!777100c9() 	
 	[Frames below may be incorrect and/or missing, no symbols loaded for kernel32.dll]	
 	ntdll.dll!77bf7b4e() 	
 	ntdll.dll!77bf7b1e() 	

...but does anyone care?