i experienced the same (pr1.3), occasionally

i thought it was webcamviewer application causing it as i had just installed that, perhaps that's not so then

more than this failure: when it happens no one can call me (they hear message that i must have shut off or sth), ALTHO 2G (or 3G) shows a distinct signal (AND: when you change signal you get "not available")

weird problem, all icons won't work, only the icon with which you return to desktops. programs can be opened flawlessly in program menu