Is anyone having problems with McAfee Endpoint Security?

We had an invalid Norton Corporate package running on our network and recently installed McAfee. Ever since, we've had problems with Outlook and IE where they would take a long time to open when first opening. About 20% of the computers suffered considerable enough productivity loss that we removed McAfee altogether. We've run boot scans on them and still had problems.

Where would you go from here? We have chosen McAfee as our AV product for ourselves and clients.