I have an O1/W with version 55 ROM. I can do everything via MIDI except it will not accept program changes from an outside source. I don't think I have any filters on, and I have loaded the factory default settings, and am sending and recieving on channel 1. Also, I can send and recieve sysex data, I can do program editing via Change It!, I just cannot get the program or COMBI number to change from an external MIDI device. What am I missing? Everything else is working fine.

Go to global mode and check and see if you have enabled the program change mode. If it is disabled you could still receive sysex messages without receiving program change messages. It may even be disabled in the original factory data. Steve Ward

You may also want to consider having the OS updated to version 62. While this may or may not address your specific problem, it MIGHT. You'll also get useful things like SMF compatibility, etc. with this version.