I don't know what's causing it, but you can go on Task Manager and right click on Windows Explorer and click restart.

Start should work for you now.

I have been using back then Avira which shown as a really good antivirus. Since the days I moved to Windows 7, I never installed any antivirus because I thought I don't need them because I am strict...

IE is actually pretty good and fast browser, but Firefox is the one which I used years ago, and will use for years aswell. Proud user of FF!