it seems to happen more to the users in remote offices, but they are not connceted through vpn. the exchange server is located here in NY. and we have offices in altanta, chicago, la, and detroit. atlanta and detroit users are getting this messages more frequetnly than others.
i was getting the same pop-up (in NY) until we upgrade the exchange to 2003 from 2000. and this server only function as exchange, there is not other data.