This has been an issue with several programmes on OpenSuSE 12.1, I expect it has to do with the OpenJDK as I have never seen it while using Java. Java isn’t available from the official repositories for 12.1, but there is some info on how to obtain it here: SDB:Installing Java - openSUSE
This is what I guess is the cause, so bare that in mind. I have not tried Tuxguitar but I have seen this error message with several Java apps, including TripleA.