open up another grphx intensive game and see if they are affected
check youre power settings
if they are on power saver or something change it to Home/Office Desk to do so, you must go to the control panel --> power options, if its on energy saver the cpu is usually starved of power.
open up a previous toribash release and see if its slow
if its just the multiplayer its prly just the server
if you have shaders on perhaps you can change the shizzy stuff off
and lastly do a clean re install or just reboot youre comp