If you've been having some problems with your connection or especially with firefox, check if you have FasterFox. If you indeed do, please uninstall this crap. I was on dnsstuff.com and got blocked by one of their script telling me I had FasterFox (which in that case was true, even though I generally don't install that thing). I was having a hard time loading pages for no reason but I had good internet download speed using FlashGet.
In the end, I removed FasterFox, restarted FireFox, everything is back fast and furious :).