I have a Xp-50 and I use it to play midi files. Some files play just fine, but once in a while some files have problems. Examples: Files will play missing tracks(Like Bass or percusions), other files only play the drum tracks, some files have problems only at the begging of the track and ususally I need to put a space before the actual song tracks. The only way to "fix" the problem is turning the keyboard off and on. Any ideas? Does the Xp-50 has a Hard Drive that might need to be replaced?