Cannot access desktop and desktop settings in Lubuntu 12.04

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http://askubuntu.com – PCmanFM is not accessible. My lubuntu desktop has become unusable: the normal desktop, handled (i think) by pcmanfm was replaced by an empty one, while pcmanfm became unstable (first used 100% of cpu, then would not be accessible at all: despite of running multiple instances ass seen below) Maybe it is my fault because I wanted to use pcmanfm 1.0 that i have installed like this but in fact for a long time i did not have any problems after doing that I have installed LXDE beside lubuntu-desktop and for a while in lxde all looked normal, but after several logins/logouts the same issues appea (HowTos)