It sounds like the 'upgrade' to your virus software might be the source of the trouble. How did you acquire this 'upgrade'? Did you download it directly from the company site? Are you
sure you connected to the right site? If you got some sort of 'email notification' about the upgrade and clicked a link in that you might have been spoofed to download a trojan, you know.
First thing to try is to go into 'Add/Remove Programs' under control panel and see if you can uninstall that recent 'upgrade' of your AV software.
After that, removing any suspicious program from the 'run' list like Iron Giant suggests is a good step. Many contemporary viruses install themselves there and watch for 'anti-virus' and 'ad-buster' software, and will
reinstall themselves after being removed! Once you've removed anything that doesn't belong from the run list you can reboot and see if Ad-aware can be run. You might also want to try something called Spybot S&D which is much more comprehensive than Ad-aware.
http://www.safer-networking.org/
http://www.safer-networking.org/index.php?page=download