Voicemail Sound files got erased!

Hello all!

I have a very weird problem, never seen that before…
For some odd reasons, sometimes vm-Old.gsm get erased all by itself! That means people can’t get their messages because when they logged into their voicemail, it says: ie: You have 2 new messages and 1 hangup. It hangs-up because it can’t find the file anymore… so the voicemail application just stop. That means no one can get their messages… It’s really annoying because it can not happen for a month and then it can happen twice in the same day… Very confusing…

Does anyone have a clue? Has someone ever seen that before?