Hi ted bear. Rundll gets the blame for a lot of problems. This is because it is a small application that is used to access DLL files, and Windows uses a lot of DLLs. The problem usually lies in the DLL being accessed. The full error message usually gives a clue as to what DLL it is that's in trouble.
What version of Windows are you using, did you recently install some software or update a driver that might be causing the problem, and is there more to the error message that you can tell us?