This is 2000 or earlier, right?

Looks like you're using a backup tool that is freezing I/O on the server to do its backups and hasn't thawed the I/O properly. This is done using undocumented DBCC commands that I don't want to divulge. The databases will be unchangeable until they're thawed again or you reboot the server (the frozon state is not persisted). Try cancelling the backups that are running.