Ugh
Gotta love it when you spend hours and hours troubleshooting a program... One machine works absolutely perfectly, the other machine works absolutely not at all, and the differences are negligible. One person works and works and works... You work and work and work... You start delving deep into the program's code and underlying functions, tweaking and debugging and dumping variables to see what's wrong... Nothing seems to work! There is nothing different! Nothing you can think of... Nothing, that is, until one of you gets the brilliant idea to copy one file... One single little file? Copy it from the working system to the broken system... And then it all works perfectly.
One file. One minute of transferring? After hours and hours of work... One file fixes it all.
I feel really stupid now. I really should have seen it sooner.