If you are getting error code x80070646 or 646 or 1606 when installing update via Windows update, then here is a quick solution. These error occurs when installing update for Microsoft Office applications.
The problem is because of incorrect registry value. This is a know issue and error can occur on windows XP, windows Vista, Windows 7.
How to solve these errors and successfully install updates:
Microsoft has release a fix for this bug. Just download the fix and run it. You may need to restart your computer after running this fix.
Download Fix For Error code 0x80070646, 646, 1606