Disappearing Microsoft Outlook Contacts - Please Help

[nj814kf]

Our small firm shares a public MS Outlook folder to access firmwide Contacts and Calendars. Every month or so, the majority of the Contacts simply disappear. The ones that are left appear to be the few that we've updated within the past few weeks. We know its not a blackberry syncing issue as we've locked down the change permissions on the PST to just a few and the problem persists. We outsource our server hosting and they have no clue what it could be. They backup data on a per user basis from Outlook and indicated it's not a user deleting them, but maybe a user could be accidently moving them somewhere. Clearly, we know its not that. We are fairly confident that the firm hosting this for us is responsible, but we have no way to prove it or ideas on what to tell them to check on their end. We've asked them to check expiration settings on the server and have had a few other ideas, but no luck so far. They also recently slipped up and let us know that another account on our server had also been experiencing data loss issues.

Any help in nailing down the source of this annoying problem would be much appreciated. Thank you.