This problem just appeared on my iMac. Seems I can't open any folders on my desktop. They can be highlighted but not opened when clicked on. Can't open any applications. Same with external devices. They appear on the desktop when connected but don't open when clicked on. Moving icons on the desktop is hit or miss, jerky at best. Applications in the dock, for instance iTunes, will open but do not function. I am running OSX 10.6.8. I've restarted, relaunched the finder and reset the PRAM. Tried changing screen resolution, too. No luck. Internet access seems to be ok. Mouse seems sluggish taking several long slow clicks for a response. Any help would be much appreciated.