You might want to check the solder joints also.
Indeed, I had that problem with the joystick port in my A2000. After heating solder on all pins (why bother with trying to check which ones aren't properly connected? Just re-do them all again) it worked without problems again.
This seemed to be even more common problem on Philips CM8833-II monitor (due to bigger stress on the connector, as video cables usually weigh a lot more)
