Written by Daniel Mundy | 27 October 2009

After uninstalling the old version of McAfee and installing the new one, some PCs were displaying this message when Outlook was opened:

The Add-in "Exchange Scan" (C:\Program Files\McAfee\Managed VirusScan\VScan\OtlkUI.20091023152755.dll) cannot be loaded and has been disabled by Outlook. Please contact the Add-in manufacturer for an update. If no update is available, please uninstall the Add-in.

The first thing to try when fixing Outlook plugin errors, particularly after uninstalling/reinstalling antivirus programs, is to delete the extend.dat file from C:\Documents and Settings\username\Local Settings\Application Data\Microsoft\Outlook.

 

If deleting extend.dat does not work, try the following:

1. Click Tools, Trust Center
2. At the bottom there is a selection list called "Manage", from there select "Exchange Client Extensions" and click Go
3. Uncheck "Exchange Scan"