Guru3D forum is one of the VERY FEW sites where I disabled adblock. Today I ran into major troubles with some ads trying to load, I remember one URL maps-4u.com or something and some others, essentially slowing down Cyberfox to a crawl, even creating some nasty artifact on my desktop. I don't mind ads when they're unobtrusive and when I think the site/forum deserves ad revenue. I am a webmaster too, I know stuff in this world isn't free But check your ads maybe, there seems to be some nasty stuff among them.
If you see them, please email me a screenshot plus the ad properties. I really cannot do anything with merely a vague description.