I am experiencing this after it disappeared in Lubuntu 12.10 from Lubuntu 12.04.
I've upgraded to lubuntu 13.04 and it appeared again.
In order to reproduce this error:
1) Kill pcmanfm from console
2) Start "pcmanfm --desktop-pref" and TICK "show menu provided by window managers when desktop is clicked"
3) Start "pcmanfm --desktop" (either with or without a "--profile" parameter)
4) Right click on an icon on the desktop
4.1) Double click on an icon on the desktop
4.2) Select an icon and press RETURN
4b) Right click on the desktop (anywhere but an icon)
5b) Does not crash
2c) Start "pcmanfm --desktop-pref" and UNTICK "show menu provided by window managers when desktop is clicked"
3c) Start "pcmanfm --desktop" (either with or without a "--profile" parameter)
4c) Right click on an icon on the desktop OR anywhere on the desktop
Basically it looks that the menu provided by lxde makes pcmanfm crash.
1) as suggested I tried to install libfm-dbg (success) but I could not install pcmanfm-dbg beacuse of the Ubuntu dependency hell. I cannot remove pcmanfm because it would tear apart my distribution nor I am allowed to install pcman-dbg because I have pcmanfm package in place.
So I'm afraid that at this time I cannot provide a useful stacktrace other than the attached one.
2) Tried running a fresh install of Lubuntu 13.04 on a virtual machine and the error never show up: I must assume that the culprit is some old GTK (?) lib from Lubuntu 12.04 or 12.10.
3) Tried cloning the current git repo and compile. That specific issue does not show up.
If there's anything more I can provide, please let me know. As a last resort I will wipe out the distro and reinstall 13.04 (I love this file manager, don't want to switch to anything else at this time).