Microsoft posted revised patches Wednesday to correct a problem some users had in installing fixes for a pair of vulnerabilities disclosed two weeks ago.

The retooled patches apply to the Windows Messenger Service vulnerability in Windows NT, 2000, XP, and Server 2003, and to a problem in Windows 2000's implementation of the Windows Troubleshooter ActiveX control.

Microsoft's original security bulletins for the two vulnerabilities were made public on Oct. 15, and were rated as 'critical,' Microsoft's highest warning level.

Some users at machines on which the Debug Programs users rights had been revoked were not able to install the updates, however, which led Microsoft to publish revised patches.

Windows users who have successfully installed the original patches do not need to re-install the new versions, said Microsoft.

Both of the tweaked patches can be obtained through Microsoft's WindowsUpdate service.