Following the release of KB 973917, many computers running Microsoft Windows 2003 R2 and having IIS 6 installed and running found themselves in an odd situation: after reboot, IIS would stop working. Application pools would crash and be disabled because of the rapid fail protection mechanism of IIS, and end users of the applications that were running on the servers would receive a black and white page saying simply: "Service Unavailable".
This is because, many customers running IIS 6 and Windows 2003 were in a situation that we usually call binary mismatch: the binaries of IIS were of a lower version than the binaries of the operating system on which IIS ran. If IIS binaries were patched to Service Pack 1 and the operating system binaries were in Service Pack 2 the system would still run until the patch was installed. Afterwards, IIS would crash and stop working. The reason for this is explained in the last blog post on this subject.
Changes to the install of KB 973917
To minimize the impact that the install of this patch would have on computers that were in a binary mismatch situation, the IIS team decided this week to change the Windows update rules on computers. Thus, now instead of offering the patch to everyone, the patch will only be offered to those computers that are not in a binary mismatch situation.
Thus, if your server is running Windows 2003 and you have installed Service Pack 2 (which you should have), you will only be offered the patch if your IIS binaries are also patched to Service Pack 2 of Windows 2003. To determine if you are in a binary mismatch situation, please refer to my last post about IIS 6 and KB 973917.
by Paul Cociuba – Senior Support Engineer on the IIS Team
KB 982666 also breaks IIS for the exact reason.