Photoshop has been running great for a while then over the last two days it has gotten REALLY slow. Basic editing it does ok with but when applying filters (especially smart sharpen) it is 10 minutes to do what took 30 seconds. Saving also takes about twice as long. I've not done anything different to the system, no new hardware or software and i have the same programs running in the background as usual (itunes, folding at home, firefox, sometimes indesign, illustrator and or dreamweaver). I've closed down all but PS and it is still slow - It's just a sudden 'random' drop in performance. I've tried resetting a couple of times and running the maintenance scripts via terminal but it is still very sluggish. Other programs appear to be running fine. Any thoughts as to what could be going on?