FYI, I heard back from MicroChip. Here is the magic steps that cured the problem. 1. Exit MPLAB and reboot WIN95. 2. Reinstall MPLAB. 3. Goto directory where MPLAB is installed and run BWCCFIX.EXE After these steps, the crash no longer occurs. I have not yet verified that the stimulus is actually working properly. So far no one has a clue about what caused this error. >Help!! >I am running MPLAB under WIN95. I tried to create and run a pin stimulus >file. When trying to open this file WIN95 crashes with a general >protection fault in BC450RTL.DLL. I chopped my stimulus file down to >two lines: >STEP RB7 >10 1 >--- Steve