Yes, S_M_A's post mentioned that already, but again, I have 2 other applications that make use of the library and they work! As far as I know, there is no "app-specific" dll registering, so if they use it, everyone can.

Running DLL Walker on the file, I get this message on my machine (where the app IS working)
Warning: At least one module has an unresolved import due to a missing export function in a delay-load dependent module.
No DLL files are marked with warning symbols, the application works fine.

Running DLL Walker on an XP machine, I get a warning symbol for WER.DLL, yet the app works fine!!!

Running DLL Walker on a Win7 machine, I got a warning symbol for IEShims.dll. I copied the file to ..\Windows\System32\ and the warning symbol disappeared, but the app still would not work.

Needless to say I feel a bit frustrated. Perhaps I'm not reading the DLL Walker interface correctly...? What am I looking for in case there is a problem with my DLL?