dont know about mororola but motorola iv heard of lol!
when your in a party on call of duty, look in the bottom right, it should say NAT Type:Open, if it says moderate or strict then that is your problem.
if its on moderate or strict, you will need to open up ports on the superhub, or put your console in the dmz
if it is on open nat type you should find out the following:
1) take a speedtest (
www.speedtest.net) and pingtest (
www.pingtest.net) NOT during the period 5pm to midnight
2) repeat step 1, but DO the tests some time between 5pm and midnight
3) if there is no difference between the two, you should take the test when cod gets laggy. take a record of what time etc.
4) make a post on the virgin media forums (community.virginmedia.com) ask them why its laggy, they might be able to find out if there is over-utilisation (or one of the VM guys on here could be so kind)
hope this helps