I installed to a XP workstation last week: VirusScan 8.5 (patch 7) McAfee Agent (ePO) 126.96.36.1990
User stated they never had issues with outlook, but almost immediately after VirusScan install they started to receive following error dialog boxes:
When opening mailbox items: Microsoft Office Outlook: Cannot open this item. Your server administrator has limited the number of items you can open simultaneously. Try closing messages you have opened or removing attachments and images from unsent messages you are composing.
When sending new emails: Microsoft Office Outlook: The Operation failed.
The user typically closes/reopens Outlook and they are good for a few hours, but then the same error messages appear again.
The errors don't seem specific to VirusScan, but they started immediately after it was installed, so I do think it has to be the culprit.