This hotfix which IS on the microsoft site relates to the pine server.
There may be an error in the header of an e-mail message that causes a problem.
It is ONLY relavent to Echange Server 2003 and no other OS.
See the article on the microsoft server here;
Error message when you try to open e-mail messages that you downloaded by using the Pine e-mail client in Exchange Server 2003: "Not a string (<Date>)"
There is however a fake email regarding this matter making the rounds so you have been warned.