I have exactly same issue and I can tell it has nothing to do with virus or computer problem. It is directly linked to microsoft update KB2691442 recently launched.
After the problem occured, I reverse my computer to previous date (with Ghost image) and I have installed one per one the 14 updates of Windows (I have W7-64), testing effect after each patch, until I found that the issue appears after I install KB2691442.
So I ghost it back again, reinstalled all WindowsUptade patches apart the famous KB2691442, and the problem is not there. No doubt the issue comes from Microsoft!!
Actually, in the past another windowsUpdate had created same problem. But I found a patch to correct this bug (so called KB980408 Fix.reg, you can find it on the web). Unfortunatly, this corrective patch is not working on the new issue created by KB2691442.
While I have a solution with not installing KB2691442, this is very annoying:
- to see that official patch from MS creates problem to our computer
- it is a safety update, and not so happy I cannot install.
If anyone has a solution (such as KB980408 Fix.reg), happy to hear
fred