Smells like a bad browser plug in.
If it was a Firefox plug-in issue, then you would think IE (which I have no plug-in’s for) would fly like a champ, but I can’t even get IE to open a web page.
Something else I forgot to mention: whenever it gets light outside is when the internet gets slower. At 3am when I get up for work, I can do pretty much whatever I want. Browsing is fast as hell then.