KB2811106 for x64 windows 8.1 ...
I'm having the same problem.
I tried to install the optional Microsoft windows update KB2911106 that appeared for my Yoga13 running Windows 8.1 but it fails to update. When trying to manually install I get the error "this update is not applicable to your computer".
I believe that users without Bitdefender have installed this update fine on the same hardware / laptop.
Have tried switching off Antivirus and Firewall but made no difference. Any other suggestions without having to uninstall Bitdefender?
Sorted, I had to uninstall Bitdefender and then this update was a success!
(Even switching Bitdefender Antivirus and its firewall OFF, would not allow the update! Must be a bitdefender bug!?)
This update came through just fine for me yesterday, no changes for BD was needed.
I don't think Bitdefender is completely to blame if at all a contributory factor. I had a failed install the first time I tried to apply the patch. It was caused by an interrupted download. Second time of asking it completed fine.
I reckon the operational state of MS patch download servers may be partly responsible.
Looks like the Bitdefender signature has now been updated for a file in this update, see link below;