Clocking at 4x. I can appreciate your point about performance (1 byte at 115200 is about 160 processor cycles with 4x clocking), but it still shouldn't lock up the receiver if it receives two bytes! Like I said, framing errors or bad data I could understand. And also, why would the other serial port work???

I'm going to try the h/w mod I mentioned in my last post and also double the crystal if that doesn't work. It may be worth doing that anyway...