App's DLL Not Loading on Debug

Question

While debugging a WinPhone app, I found that symbols weren't loading for my app's DLL, and further research showed that the DLL wasn't showing up at all in the Modules window during debug - it's like it (and a few other non-Microsoft DLLs) were simply not bothering to load.  Not just the Symbols, but the DLLs themselves.

When I simply copy my code over to a new project (the project is small) everything works fine; all the DLLs load appropriately and I'm able to debug and set break points.  What I'd like to know is what might be causing these DLLs not to load.  I haven't done any "weird" tinkering with settings, and any restarting of the IDE or deletion of lib and bin folders haven't made any difference.

Any tips or thoughts on this front?

Thanks!