I've got an absolutely fresh Windows 8.1 Pro x64 English UEFI which seems to work smoothly.
First of all, the preinstalled Windows Update client doesn't work at all today - just checking for updates for ages - until KB3138615 is installed.
When I am finally able to check for updates it appears that there are about 300 updates available with KB3000850 November 2014 update rollup among them, which requests KB2919355 already installed and forces to download KB3003057 and KB3014442 as it requires them also.
As at the moment I know nothing about KB3000850's craftiness I just select all the available updates and wait a couple of hours until the update process finished.
When my PC is ready I notice that the Welcome screen now takes 16 times longer (24 turns of welcome circle after vs 1.5 before) and there is 2 minutes 30 seconds of black colored emptiness between the Welcome Screen and the desktop appearance.
After some research I've found out that both delays are caused by KB3000850.
When I've downloaded each required update to install KB3000850 then no matter if I restart my PC after each update required by KB3000850 (including KB3000850 itself) or install them all during the same session I have the delays.
Also seems that installing all available updates through Windows Update doesn't solve the problem.
Delays appear each time I turn on or restart my PC when KB3000850 is installed.
Additionally I can no longer install KB3138615 after KB3000850. In this case KB3138615's standalone installer behaves exactly like Windows Update before applying KB3138615 - it endlessly checks the computer for installed updates.
How can I reduce the time taken by the logon process? I appreciate any suggestion other than "ignore KB3000850."
(I've researched a lot before asking, but the only troubles connected to KB3000850 were related to different kinds of crashes after applying this patch.)
The question: How can I get rid of that ~3 minutes pause between the logon screen and desktop appearance?