High Speed running too slow

I have broadband thru Comcast and I have been very satisfied with
it over the last seven months. About two weeks ago I noticed that
no matter what website I go to there is roughly a 15 to 20 second
pause before it downloads the page. When it downloads, everything is fine
even streaming video, but click on another link and once again it pauses
then downloads. I contacted Comcast and they said it must be my computer.
I question that because it does it using both Safari and Firefox and with some of the widgets. I have only one computer so I'm not able to mimic the problem. Any suggestions?

MacIntel 17" 1.83 Ghz - Version 10.4.8 - Updates are current.

Thanks

 

Great website - My results were 33% worse to 37% better depending
on the server.

Thanks