Microsoft fixed one of its July patches this week after reports that the patch appears to install correctly, but then is reoffered by Automatic Update and Windows Update.
The patch had been released last Tuesday to fix a vulnerability in Internet Information Services (IIS) that use Active Server Pages that could allow remote code execution.
The original release was part of seven patches distributed by Microsoft as part of its monthly Patch Tuesday release cycle.
Issues with the patch occurred because of the way Windows Update determines which computers should be updated, according to an advisory released by Microsoft.
Windows Update then offers the update to PCs that have IIS common files installed, but do not have the Asp.dll binary.
In another issue, ISS also locks the Asp.dll file, preventing the update from installing correctly, according to the update.
A Microsoft spokesman offered a post on the Microsoft Security Response Center blog as a statement. It advised Windows Service Pack 1 users to rerun detection to make sure their systems have updated correctly.