Dlls working and then not working

I have an issue with several softwares.

They use the same dlls.

Now sometimes the program loads up fine no issues.

Then the following day Il start windows, run the program and il get an error saying its had a problem defiining one of the functions in the DLL.

Now these arent COM dll's but most likely made using Pascal, C, Delphi or assembly code.

Now the question is why would this happen. Is the Dll having mood swings? or is there something running (or not running in background) that could cause this?

If I gave a link to DLL would that allow anyone to have a look and figure out why?

Can you give more specific descriptions of the dlls and the softwares? Where are the dlls located?

dll in application folder.

dll made using c or assemblycode

the dll accesses windows api functions and checks if a specific window is active/visible

It seems you've posted in the wrong forum. I'll help you get your thread moved to the proper forum by notifying the moderators.

Who created the DLL's in question?

The answer to that question is in a better position to answer your question than any of us are.