[RoSs_bg2_rox]

It is most likely nothing to do with your ram, unless of course it only does this in busy areas.

Sounds to me like it's your Ping. Wireless isn't the best for gaming, and especially going up two floors, you lose a lot of signal. Is it a 54mbps card you use? Definately if you have limited connectivity this would sound like the problem - would it be possible for you to move the router when you game? Or put it on the middle floor, or something to get it closer to the card. There are also various signal boosters you can buy, or you can make your own, the easiest / most common way being with a pringles can.