Microsoft has admitted that users who installed the security patch for Windows 98 and ME in January are suffering from slower machines or frozen screens as a result. The MS05-002 patch was issued by Microsoft for the Windows 98, Windows 98 SE and Windows ME operating systems as part of its monthly patching cycle.
The problem relates to the way the Internet Explorer browser works with the operating system. Removing the patch returns the machine to normal performance but leaves users open to security vulnerabilities, although Microsoft said it had not yet received any reports of exploits of these vulnerabilities.
More...Microsoft admits patch problem
and...Plug More Holes
According to PC World magazine (June 2005), Micro$oft is studying the problems so there is no patch for the patch.
I have had the patch installed on my PC for some time with no problems to date.