Welcome back nathanb.
Please make sure that you entered the right IP...
The next time you're experiencing lag on the game, please do the following:
Goto Start, Run, type CMD and press 'OK' - now type: PATHPING 126.96.36.199:21015 (Ensure that this IP Address is correct...) - please copy and paste the results by right-clicking on the Command Prompt window, selecting 'Select All', and then pressing Ctrl+C. Please post the results here.
Whilst experiencing lag, also do: Start, Run, type CMD and press 'OK' - now type: PATHPING Yahoo.com
Along with this, attempt to do the two above commands at random intervals (ie: when you aren't experiencing lag).