Phil, Hoster does not have anything to do with the sounds, so no need to reload. Check your mouse settings in the control panel. Maybe something in there controls sounds for it.
ADMIN NOTE: Good advice, but this beep is a Vista BUG! Read on...
Are you refering to a customer import as those unfortunately don't come back after a crash and have to be re-imported. If it was one of your loaded songs then you may have a corrupt file for that song.
ADMIN NOTE: That's incorrect. If you have imported songs into your Playlist from discs your Singer's bring in, they WILL remain in the playlist and on the hard drive after a crash and restart of Hoster. All will be fine, in the same order, ready to play. That's part of MTU's Failsafe design to keep your show running even after a crash. 
NOTE: Once an imported song plays it's imported image is deleted, AND... when Hoster closes normally, all imported CDG tracks are deleted to keep you legal, yet allow you to play tracks from your Singer's discs.
If you do reload Hoster it will not erase your database or the song files.