I also recently tried the new version and was disappointed, seems like a big step down, I understand a lot of the changes were to support vista and a fancy new gui.
I won't use any program on a regular basis thats a memory hog, and I too had several problems updating, uninstalled and removed it from registry and reinstalled, closed all background app's, etc, but still had the problems, if I closed adaware, reopened and tried again several times it would eventually go through, server load or a bug who knows.
Then adwatch was eating a lot of ram or so and I disabled it in adaware.
Then I noticed it had a service added, so I set it to manual only to run when I run adaware like I do with some other programs.
Then the program wouldn't run unless I manually started the adaware service, fine for me since I only wanted it as a backup scanner to use once a month or so.
The services purpose is to give admin rights to the program, since it can't run on a limited user account in vista. Gone are the days of using adaware as a good backup spyware scanner for me due to the memory/update problems.
I figure I have enough security on my pc anyway with better anti-malware programs like AVG anti-spyware, A squared, spybot, windows defender, spyware blaster, and hijack this I shouldn't need it but always nice for people to have several good free scanners to use.....but a shame since the old version was so good.