Mattaeo,
A full factory restoration through the function page is the best way to go, but you will loose all your data. In order to do this, you must place a check-mark in each box, then press the "D" key to bring the keyboard back to where it was when it came out of the box.
If this doesn't solve the problem, then you may wish to do a complete system check. You can find the details on this at the PSR Tutorial. Here are the basics:
1. Power off
2. press C2# - F2 - G2# (all three together) and while keeping them depressed,
3. switch the power on.
You'll see the word "TEST" on the display
With Tempo - / + you can go to the test you want to perform. Start/Stop will start the test. Wait till a test is done!
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Travlin' Easy