Vista - Painfully slow network speed

I have been using Vista with my many builds on my Inspiron 9300. My wireless
connection has been great. Now since I’ve been using RC1, my network
connection has gone down to a crawl. I’ve been testing my speed on
http://speedtest.net and my connection is getting around 56kbps down and
512kbps up. Prior it was around 4561kbps down and 500kbps up. Something
has happened and I don’t know how to track this down. On a windows XP
machine using same internet connection my speed is similar to the speeds I
was getting on the previous builds. Any help would be greatly appreciated
because I am very tempted to wait until the final product before using Vista
again.

Thanks for any help