After disabling the "Delete All" option in the PM inbox, "some" users were unable to login to the forum with a message saying:
Sorry, only members with sufficient permission can access this page.
A security error has occurred with authentication.
Please ensure that all cookies are enabled on your web browser, and you are not using a saved or cached copy of the page.
All I did was, I added (') in front of this line to disable the delete all option:
Response.Write("<input type=""submit"" name=""delAll"" value=""" & strTxtDelete & " " & strTxtAll & """ />")
Does this have anything to do with that login problem?