Just passing on what happened to me on Friday /yesterday. Had a message that there was a new Skype upgrade available (to v.220.127.116.11), so I upgraded, and then toddled off for supper. Came back and briefly used the PC before heading of to bed - the PC response was sluggish, and left click slow at best, so I made a mental note to change mouse batteries in the a.m. as that's what the problem looked like. Next day the PC was varying between being completely spastic and OK. At first I thought the new batteries I'd put in the mouse were shot so I binned those for more new ones, but the problems remained. I tried shutting various processes to identify the problem, but nothing was apparent as the cause. As the only change I'd made before the problems started was to upgrade Skype I decided to un-install it completely and do a clean install - problem solved.