Last night I installed some applications and updated my Ubuntu 12.04 LTS,since then I encountered a strange right click problem, that is my right click is not working but when I open home folder from launcher right click works again.

Actually problems starts last night when my desktop wallpaper changes suddenly to Ubuntu default, when I tried to change wallpaper I find that my right click is not working.

I tried to reboot system but that also not solved my problem,i clicked here and there but when I opened the home folder my wallpaper changed again to previous one and when I checked the right click it is also working.

Now the problem is that this problem comes back again whenever I turn on my system,and also whenever this problem occurs the Ubuntu desktop menu bar also disappears from unity top panel.

Don't know what is really going on, please can anybody help me.