I built my cabinet about 17 years ago.  I got the HAPP USB trackball that also has the PS2 adapter.  I've only ever used the USB connection.  It has worked fine, although I haven't used it in many months.  I tried today and it only goes up and down.
I tried the PS2 connection and it doesn't seem to work.  I tried it with my laptop and it has the same issue.  So I'm guessing the issue is with the trackball itself and not a software setting.  
I was going to remove it but that will require me to fully take out all the buttons on the control panel and I would need to spend serious time labeling everything first.
Is there anything I could try or do I need to track down a replacement?