Hi,
According to my log files the forum "activity" was manually "pruned" with no value for "the number of days since last post" field. I'd already disabled the "auto pruning" feature in the administration area but I missed the manual pruning options!
Needless to say it's been taken care of now but that won't bring back the messages!
Any idea how many posts were lost? If it's thousands, I may be able to restore some/all from backups but it's quite a big job so there would need to be lots!
Hope this helps,
Andy