I just rebuilt my system and when I installed Acrobe Reader, the new version was 8.1.1. My ISP provider is Hughes (2-way satellite). I found that after accessing a PDF on-line, the Hughes modem got choked up somehow. Evenually, I found reference to a possible problem with AcrobatUpdater.exe which apparently checks for updates as you exit a PDF. I found Adobe KB article kb401737 which resolved my problem. But, of note, my system did not show 100% CPU usage, only the choked modem.