As many, I had the same problem with no idea why!! After reading many of the options here and feeling just as sick of it. I lost a full day as I tried changing the rights of programs in my AVG Pro, Changed ownership five times of my two expansion drives & my drive "C" Done a complete rebuild of my index, and altered it many times.
NOW THE GOOD NEWS FOR YOU.
I followed the advise of "rastermanx" and;
In "Customize Start Menu" options (of Taskbar and Start Menu Properties), set 'Search other files and Libraries' selection to SEARCH WITHOUT PUBLIC FOLDERS. Then click OK twice.
Just in case like me you don't how to get to the Start Menu options; Right click on the Windows start icon and go to "Properties" and your in.
Thank you "rastermanx" you are a God of all Gods.