Problem with digital/optical audio output from Mac Mini

I recently bought a Mac Mini (4GB RAM) to play FLAC and ALAC files into my stereo system. But I have run into a problem.

I have played FLAC and ALAC files using Songbird, VLC and iTunes. I am feeding the digital audio out from the Mac Mini via Toslink to the digital audio input on the back of my pre-amp.

The problem is that as each song finishes in a playlist or during an album, there is a 1-3 second break in the audio input. This is evidenced by the L/R input indicator lights on the front of the pre-amp going out (like the input signal was temporarily lost), but more importantly by the first second or so of the next song not playing. The lights always come back on but I've missed the first second or two of the new song.

I am using other Toslink audio inputs into my pre-amp from my DVD player and Cable TV box, both with no problems.

I have tried changing out the Toslink cables and switching the Mac audio output into the other 2 pre-amp Toslink inputs with no success.

Also, I tried a 3.5mm-to-dual RCA jack splitter and ran the analog audio out from the Mac Mini's headphone jack and the break does not happen and the new song plays fine right from the start. (the input lights stay on on the pre-amp while one song ends and the other starts).

I have tried different software audio players (iTunes, Songbird, VLC) and this happens with all 3. I have also tried both ALAC and FLAC files, which play fine on another computer (i.e., the song files definitely are OK).

I have tried playing with the gapless and crossfade settings in iTunes but I think the issue is with the digital/optical audio out from the Mac Mini or it could be how my pre-amp is handling the audio input via Toslink.

Paul