For What it's worth, I'm on Windows 7, Aurora is in my Program Files (x86) directory, and I'm seeing the Error 76 followed by infinite Error 91 problems other people are reporting. I doubt it's helpful, but looking at it in a debugger looks like the call stack is bumping back and forth between Aurora.exe and msvbm60.dll.
EDIT: Just to test, I blew away my copy of Aurora, reinstalled 4.91, and then installed the 5.4 patch over that, and the behavior is still bad in the same way.