The latest upgrade for McAfee's VirusScan Enterprise security software is causing problems for certain versions of IBM's Lotus Notes email application, the companies have warned.

The issue affects users who have upgraded to VirusScan Enterprise 8.5i and are using the R6 or R7 version of Lotus Notes, McAfee said.

While working in Lotus Notes email for a period of time, typically an hour or two, the program will display the following error message when users try to open or delete email: 'You are not authorized to perform that operation'. Users can close the dialog box but then can't do anything else in Notes.

Notes can be restarted, but the error appears again after another hour or two, IBM said in an advisory.

To avoid the problem, the companies recommend disabling two settings in McAfee's software: 'scan all server databases' and 'scan server mailboxes'. McAfee posted instructions on how to disable the settings in its advisory. Affected users should contact McAfee technical support.

IBM said another option is to disable VirusScan Enterprise completely – although clearly that may have security consequences.