Ubuntu :: Big Slow Down After Update - Took 3 Seconds For The Mouse To Select The Pic

I have Ubuntu Lucid Lynx since it came out, and until now it worked fine. I am updating regularly. Today too, I installed everything offered to me by updates manager (I looked through the list and didnt see anything I wouldnt want to update, but I dont remember everything that was there), and it asked for restart. Ok, so I restarted. Everything seemed fine. Then I tried to look at a picture, in normal,default viewer, an huh. It took 3 seconds for the mouse to select the pic, then another about 6 to open the viewer (and we are talking about a 40 KB pic). That was slow, but I thought maybe it was an accident. But no, everything I tried since goes slowly, at about a quarter of speed as before the update. I tried to remove unnecessary things with apt-get autoremove, I tried to stop or end all processes that seemed unnecessary, with no result. I restarted thrice. Nothing comes to mind anymore.