Security vendor McAfee slipped up this week after it was discovered that the latest version of its VirusScan Enterprise suite had locked IBM Lotus Notes users out of their mail.

McAfee VirusScan Enterprise 8.5i has been generating 'undiagnosed errors' and lockouts in Lotus Notes.

The security firm said that it is investigating the issue and suspects that the problem might actually be a "feature".

"A new feature in VirusScan Enterprise 8.5i is incurring a problem with the Lotus Notes client while attempting to scan the server-side mailboxes," the company warned.

The option to scan server mailboxes is enabled by default, and McAfee said that 'scan all server databases', which is disabled by default, may also be contributing to the issue.

One workaround may be to disable both features, but IBM has other ideas. The company stated that if users see a dialogue box saying 'You are not authorized to perform that operation' they should completely disable the antivirus software.