WinXP- desktop not clickable

When I go to double-click a desktop icon, sometimes the application does not launch, and afterwards none of the icons are clickable. The mouse can be seen moving around the desktop, but I can’t left or right click. All I can do is click the “Start” button, which brings up the start menu (including the log off and shut down items), but none of the items on the start menu (including shut down and log off) work. I have to reset the computer to get it to turn off and re-boot. The desktop icon that I double-clicked is left highlighted as it normally is when it works. This occurs somewhat randomly, although it appears that it’s a web link that I’m trying to open when this happens. Any help much appreciated.



WinXP SP2, IE7, AMD 4800+, 2BG Corsair Ram.