Sorry for not seeing this message earlier.
I don't think it was a problem with the ad-aware but a problem with permissions to run the adaware service. awservice.exe is the service which runs automatically at the background when you install Ad-Aware. By looking at the message it seemed that Vista didn't want it to run and kept asking your permission.
Uninstall ad-aware would have helped and re-installing (which you eventually did) however I would have gone into the services window and would have set it to "Automatic".
Here how you could have done it.
1: Click Start (that blob thing which has windows logo on)
2: Click Run
3: type Services.msc
4: Search for awservice.exe
5: right click on it and click properties
6: select automatic from drop down menu and click apply.
Saying that sometimes awservice.exe is a spyware too. In that case you could run Spybot or Malwarebytes onto your computer (both are free).
AVG would only catch spywares if you are using their AVG Internet security package, not Free version.
Personally I wouldn't use Ad-aware as it is not as good as Malwarebytes