Steveman,
Yes, the problem could be a 16-32 bit issue, especially if the underlying system prototypes API calls or functions from other DLL's, such as a third-party.
I can't really tell you which file to look at, having no idea of the system itself. Try to determine which form triggers the error and then see if you can open it's .FSL file in a Design window. (There's an option on the File | Open | Form dialog.)
Before you get carried away, go into Developer Properties and make certain that the Advanced button is selected for ObjectPAL. This will display all the available methods that could contain code.
Once you get the form opened in a Design window, press Ctrl+Space to display the Object Inspector and then open an editor window for one of the available methods. It doesn't matter if there's actually code in there or not; we're trying to add a wee bit of information to what you've currently got.
Once you get an editor window, look for a menu command called Compile with Debug. See if it's checked. If not, choose it and then save your form.
That done, press F8 to run the form and then trigger the process that's currently displaying an error. This should provide additional information about the method and line that the error is occuring on.
Also, when the error dialog appears, take a moment to see if the >> button is enabled; if so, that means there's more specific information available. Click it, write everything down, and then post it.
We should be able to make some suggestions from there.
Hope this helps...
-- Lance