Path/File Access Error

I have an application that has been working in a Production environment for a few years now. I need to make some tweaks to it and I'm at the testing phase and all of a sudden, I'm getting a Path/File Access Error with the filename in question being one of those vb*.tmp files (it's a different filename every time). The program has 1 main form and creates 8 copies of a second form that run the code for 4 different database tables. The code gathers the info from the database columns, manipulates what it needs to in the VB code, then adds the records to a CDO Rowset which gets passed to Crystal Reports (version 8.5). The path/file access error occurs on the line that reads:

Set rptReport = New crReport

(crReport is DSR File)

The 4 different instances of that second form are running asynchronously. Could it be that it's just stepping on it's own toes? Why would it start happening now, all of a sudden, and not within the last few months or years since the app has been running (it runs 24 hours a day, every day). And it only seems to happen in the environment, not in the actual compiled version (although sometimes the compiled version just locks up for no apparent reason).