Changing a DLL that is used by an Agilent Vee Pro 6.01 Compiled Program

Question

I have an executable that looks for a particular DLL. I have changed the source for DLL and recompiled it (written and recompiled in VB6). Once I replace the DLL, the executable hits a runtime error when it gets to using that particular DLL. Works ok when I recompile the executable.

So my question is, with same DLL path, same name, and virtually identical DLLs, why does the executable need to be recompiled?

This is driving me bananas so any thoughts would be appreciated. Thanks, Callum.