I recently bought a new system and was having severe disconnect issues.  I could play for about an hour, but then would be disconnected from the server.  I could re-connect, but it would only last a few minutes before being disconnected again.  I would ping the server to see if I was losing network connectivity... my results were I would get some negative ping results (-2ms, -5ms, etc...).  I was going insane trying to figure out what the problem was.  I happened by the following link which described my issue perfectly. 

So, if you have a dual-core system that is disconnecting you, try this fix - it worked for me.

http://www.dslreports.com/forum/remark,15398295