A couple of weeks back I had a problem with both my slides and music skipping and pausing. I followed the recommendation repairing the library.
It continued so we visited Apple and they recommended a hard drive replacement. So once we got the new hard drive a restore was done for all our files including pictures in IPhoto. We also installed the recent update to IPhoto 11 - version 9.3.2, and was are operating with Lion 10.7.3.
We re-created the slideshows with the same music and pictures and although the pictures move along fine, the music still skips and pauses (for 1-2 seconds). Some of the music is from our ITunes Library and some is from the stock music available with the slideshow feature. With either, it skips and pauses. I have checked the Itunes we are using and they play fine in ITunes. We have even tried different music, with the same results.