semi-recently UO started running really badly for me. client.exe would take up 100% cpu and my cpu fan would go absolutely bonkers. I ran a hardware diagnostic on my computer and found that the video card fan had burned out. Turns out my vid card fan was dead, which caused my GPU to overheat, so my CPU got stuck with too much work to do (my best deduction). I replaced the vid card fan and UO is running like it used to. I hope this helps someone else out.