There seems to be some problems with DNS servers lately. I am on Comcast and started noticing problems a couple of weeks ago. After some googling, I found a Comcast page which explained what was going on...

Apparently Comcast has implemented DNSSEC which is some form of secure DNS which requires some sort of authentication before accepting a response to a DNS querry as being authoritative. Many DNS servers around the net are not yet supporting DNSSEC, so their DNS responses are not accepted by Comcast's DNS servers. It was causing all sorts of problens on my end.

Until DNSSEC reaches a more wide-spread deployment, I am bypassing Comcast's DNS servers. I changed my router to use Google's DNS servers at 8.8.8.8 and 8.8.4.4 ... I noticed an *immediate* increase of performance. I'm not thrilled with using Googles DNS servers, but hopefully this will only be temporary.

Bottom line: Try configuring your PC and/or router to use some other DNS servers. The Google addresses above work pretty well. If you find other open DNS servers that work well, please share the addresses here. I believe AT&T has some open servers also, but I don't remember their addresses.