Please Help. I have a function SwapWord(...) to swap a WORD received from USB. It builds w/o any warning. But if I start debugging, the IDE pops up a message window saying that "cannot load load file 'C:\Keil\MyPrj\fw'. Debugger aborted!". This happens even if SwapWord(...) does nothing. But if I comment out this function and its references, then everything works fine. I have another similar function SwapDword(...) which does not cause any problem. I searched the forum and found this also happened before. What's the real problem here? Thanks for your time & help,