the squeezeboxserver deb requires mysql-server-4.1 or -5.0, while Ubuntu 9.10 (Karmic) only supplies 5.1, so the upgrade process uninstalls squeezeboxserver and it can't be reinstalled.

Perhaps making it just depend on mysql-server would prevent this in the future, but for now, just allowing mysql-server-5.1 would do the job. I manually hacked a deb to do this and so far the server is working fine.