Did you also install a router with the broadband? You may be running into a problem with that and packets being blocked due to the huge flood of information coming it all at once from many different sources.
If there is a "Gaming Mode" on the router flip that on. Also please make sure you go here: [link=http://support.steampowered.com/cgi-bin/steampowered.cfg/php/enduser/std_adp.php?p_faqid=246&p_created=1095497834&p_sid=T4mg_bqi&p_lva=&p_sp=cF9zcmNoPTEmcF9zb3J0X2J5PSZwX2dyaWRzb3J0PSZwX3Jvd19jbnQ9MjUmcF9wcm9kcz0mcF9jYXRzPSZwX3B2PSZwX2N2PSZwX3NlYXJjaF90eXBlPWFuc3dlcnMuc2VhcmNoX25sJnBfcGFnZT0xJnBfc2VhcmNoX3RleHQ9cm91dGVy&p_li=&p_topview=1]Click![/link]
There's a test there that may be able to help you out.
Edit: Completely broke the forums with that link! Made it into an actual link this time ;P
I did that scan and I think I just have to unstall the old way I got online. The scan said that it failed the background process and it told me to delete stuff and I did and its still not working. I'm going to have a friend come over and check it out soon.