If you were wondering why your computer was sitting on the "Stage 3 of 3" screen for hours after installing last Tuesday's patches, we have an answer. Or at least an official culprit.

Microsoft originally issued KB 3020369, the optional "April 2015 servicing stack update for Windows 7 and Windows Server 2008 R2," patch as part of a decidedly out-of-band group of seven patches on Wednesday, April 29. For reasons that aren't clear (and certainly aren't documented, as far as I can tell), the patch was re-released as part of May's Patch Tuesday, May 12.

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Shortly after those patches hit, people started complaining that installing the patches led to Windows 7 getting stuck on re-boot, with the notice "Stage 3 of 3. Preparing to configure Windows. Do not turn off your computer."

As I explained last week, the computers would sit for hours and hours -- and the only way to fix it (predictably) is to turn off the computer, or use a Ctrl-Alt-Del. Knocked out of its stupor, Windows seemed to recuperate with no ill effect.

At the time, I mentioned one Answers forum poster who narrowed the list of potential bad patches down to KB 3020370, KB 3045645, KB 3020369 (which I erroneously identified as KB 3020269), and KB 3013531. Ends up, they were right.

Microsoft has just updated its KB 3020369 Knowledge Base article to say:

Restart stuck on "Stage 3 of 3" After you install update 3020369 together with other updates, a restart may be required to complete the installation. During this restart, you may find yourself stuck on "Stage 3 of 3." If you encounter this issue, press Ctrl+Alt+Delete to continue to log on. This should occur only one time and does not prevent updates from installing successfully. An update installation fails after you install update 3020369 When you install update 3020369 together with other updates, you may encounter a timing issue that causes the update tried immediately after you install update 3020369 to fail. This issue only affects the update tried immediately after update 3020369. As soon as update 3020369 is installed, another try to install the failed update should be successful.

There's no indication at this point if the patch will be re-re-released, or if Microsoft will just let customers figure out that they have to pull the plug, after staring at the "Stage 3" screen for a few hours.

t/h Rod Trent WindowsITPro