Thanks for your reply tbworld.
I managed to replicate the error - it only happens when at least one user is viewing their pms.
There are similar complaints posted on other boards about the same issue
http://forums.devshed.com/php-develo...ng-937807.html
Please suggest your method to "trap" the error.
--------------- Added [DATE]1384231175[/DATE] at [TIME]1384231175[/TIME] ---------------
I put $userinfo['values']['do'] == 'updatefolders' instead of $userinfo['action']['do'] == 'updatefolders' and the error message no longer shows.
Thanks to everyone who responded.