You're sure that's all it says?

There should be a file called "debug.txt" inside your Halo Custom Edition directory. Open it up and copy and paste the contents of the last block (should start with "tool pc 01.00.00.0609" or something like that).
Oh forgot bout debug! yea their was aLOT more:
06.13.10 22:19:50 tool pc 01.00.00.0609 ----------------------------------------------
06.13.10 22:19:50 reference function: _write_to_error_file
06.13.10 22:19:51 reference address: 42ca20
06.13.10 22:19:51 Couldn't read map file './toolbeta.map'
06.13.10 22:19:52 EAX: 0x6C61685C
06.13.10 22:19:52 EBX: 0x00000040
06.13.10 22:19:52 ECX: 0x00000000
06.13.10 22:19:52 EDX: 0x00000004
06.13.10 22:19:52 EDI: 0x001297D8
06.13.10 22:19:52 ESI: 0x6C61685C
06.13.10 22:19:52 EBP: 0x001297CC
06.13.10 22:19:52 ESP: 0x001297B0
06.13.10 22:19:52 EIP: 0x0042D036, 8B 48 04 8B ?????
06.13.10 22:19:52 77974460 ?????
06.13.10 22:19:52 EXCEPTION_ACCESS_VIOLATION