A common theme from the posts i read this morning was Norton internet security blocking games . Then you respond you are on norton :P . would seem coincidental you are on norton , turn auto rules off ..eg make changes to norton and about the same time you encounter/notice problems .
There are plenty of free trials for DECENT security software available . As i understand it a condom over your Lan cable is as effective as norton :P :P and will free up 40% of your system resources :o
On topic though If i were encountering such problems i would fully re boot my router via control panel then double check my internet setup in winblows. if that didn't solve it i would download and try new security software switching off the old .