I have UAC turned off, I run these instead, just thought I'd toss this out there:
Avast! Internet Security Suite (very good firewall and kitchen sink for all the rest for anti-virus/malware/spam) Downside costs $, but I did a 3 year/3PC license at reasonable cost.
WinPatrol (free or some $ for lifetime database online info option, I like it)
BoostSpeed 5.0 ($30) [trial available]
TuneUp Utilities 2010 (snagged at Target for under $20 for 3 PC version!) [trial available]
and these 3 free versions for extra protection as needed: (run weekly at least)
Spybot Search Destroy
Malwarebytes' Anti-Malware
Spyware Blaster
This stuff has a lot of browser protections automatically put in play, including my Firefox, I am having no internet issues.
Here's Boostspeed's tweak screenshoot for UAC, I like the wording!