After removing old Symantec Antivirus and installing Endpoint this sometimes happens
Symptom: User encounters error,
"Add-in Symantec Anti-Virus (X.X) cannot be loaded and has been disabled by outlook."
Solution: in Outlook '07
Open the Tools menu in Outlook 2007, select Trust Center
On the left select "Add-ins", on the left right pane at the bottom in the "Manage" combo box select, "Exchange Client Extensions", Click on Go
Uncheck "Symantec AntiVirus (X.X)" and/or "Symantec AntiVirus Outlook Protection"