We recently installed Sharepoint services on out Exchange server, since then once to 3 times a day all users on the network will get an error in outlook "Cannot connect to Exchange Server", at first the message would not go away unless we rebooted the server, we have since found that restarting the Exchange services also fixes the problem, however this is only a temporary fix.
I have uninstalled Sharepoint from the server but it has made no difference.
I have run the DCdiag and Netdiag utilities, the dcdiag comes back with an all clear except for advertising test, it fails on the server as is not advertising as a time server, but the Netdiag comes back fine.
There are no events in the event logs to show a problem with Exchange, or anything else on the system, it appears to be running fine. When the problem occurs you can ping the server by name and ip, you can also connect onto it remotely.
Both Windows Server 2003 and Exchange 2003 are at the latest Service Pack, with all the latest updates. The Hardware is a HP Proliant ML350 G4, Zeon CPU@3Ghz and has 1Gb RAM, the exchange databse is 21.6Gb.
Is there anything else I should be looking at, or any ideas on what could be causing this to happen, I'm not sure if the Sharepoint install is a coincidence or if it caused the problem?