If yesterday was Black Tuesday, today must be Crash Wednesday.

I'm seeing lots of reports of problems with KB 3004394, which modifies the Windows Root Certificate checker so that it looks for bad root certificates daily. As usual, there's no confirmation from Microsoft about the problem, no documentation that I can find, and no advice on how to proceed. Users with problems find they go away if they uninstall the patch.

Lead3 started a thread on the Microsoft Answers Forum on Tuesday that described two problems with KB 3004394:

All MMC functions (Event Viewer, etc.) now require Administrator action, although in an Administrator account. Windows Defender service will not start. The Windows Defender Service Terminated with the following error %%-2147023113

In the same thread, Thinger123 reported:

After I install it, I can't install any other Windows Updates. I get an error message on Windows Update. I have already did some advanced troubleshooting and narrowed the problem down to KB3004394. The update itself installs fine, but after a reboot, no other Windows Updates will install. As soon as I clicked Install Updates on other updates, it goes right to a red X and error message. Removing the update and rebooting allows all other updates to complete as usual.

And q454 posted:

I'm also having problems with update KB3004394. everytime I try running taskmngr it kept asking that an unknown program wanted to make changes. I try going to msconfig and got the same thing, then went to UAC settings and got the same alert. basically everything that had to do with Microsoft UAC gave me an alert that an unknown program wanted to make changes to my pc

Tim Birming said:

MSE installation also aborts with error 8004ff91 after this patch. Error code reveals nothing.

And KellyPratt noted:

VirtualBox went back to working after I uninstalled this update.

The AMD forum is alight with problems installing the AMD Catalyst Omega driver. Poster necrophyte said:

with kb3004394 not installed (but all other patches from yesterdays patch tuesday installed), ran ddu, rebooted, installed 14.12 with no issues, rebooted, and now finally after 11h of hair tearing i have a functioning display driver again, even better, the omega one.. blame microsoft for this kb3004394 root certificate update, which almost made me do an OS repair install.. hope theyll read my technet thread where i first mentioned kb3004394 being the culprit

The KB 3002339 problem, by contrast, is relatively innocuous. SnydrRydr posted on the Answers forum:

I have been installing the Update for Visual Studio 2012 (KB3002339) for over an hour now and it's still not done. I took a look at the support article and it looks like it's a small bug fix update. So why is it taking so long to install?

W Jezewski offered a solution:

I ran into the same issue with three machines. Manual download and install did the trick.

You can download KB 3002339 directly from the Microsoft Download Center.