Actually, I've been looking into that problem.

What seems to happen is that the player seems to restart or reinitialize for some reason. The serial port settings are actually changed, and hijack notices the player restart and seems to forget about the bindings for the userspace app. Because gpsapp isn't getting anything from the serial port (wrong baudrate) and isn't seeing any key presses, it just sits there, frozen.

I could also be completely wrong, but this is what I had one time it froze up. Gpsapp was still running just fine, waiting for input that never came.