If you continually monitor through the fireface, that is, you don't use the onboard sound card whatsoever, likely the problem would be due to a high samplerate. MP3s and wave files generally playback at 44.1kHz unless you recorded them at a higher samplerate. So if you have your fireface set to record/playback at 48kHz and you play a 44.1kHz file, the song will be played noticeably faster than normal.

That would be my guess anyway.

thanks for your reply. I´ve set the Fireface as master at 44,1 sample rate too and this is not the problem. The strange thing for me is that this happens at certain time, a few minutes later than start playback, and with all software, nuendo, windows media, winamp, premiere etc... I´ve disabled the mainboard soundchip also.?????