AV 2009 Won't run

Hi All and here's the problem.

I have a computer on a network that I installed AV 2009 on it made a full scan, after like 15 days, AV 2009 wont start and the icon tray disappeared + outlook won't connect to the mail server + IE searches and navigation will be all messed up and redirected to different / not similare site.

Now

For the same person, I bought a new computer, installed New OS (by the way XP sp3), installed NAV 2009, after 3 days the same thing happen to the new computer, No NAV 2009, No Outlook, No IE...

Any suggestions....