Spotty internet/ xbox live connection... Help me?

ok recently my cat chewed on one of the cables for my belkin router. When i went to the store to buy a new cable, the guy there recommended that i just buy a new router. so I did, and I now have a brand new cisco valet plus. and my modem is a motorola surfboard. its old, but i have never had any problems with it before. Ever since I set up the new router, my desktop computer that is connected by hard wiring works fine, yet all of my computers connected on wireless have a perfect and quick connection that is very spotty. I will be browsing the internet perfectly one minute, and pissed off the next. Sometimes turning Airport on my macbook pro and turning it back on works and sometimes it doesnt. Sometimes it will say that I am connected to my network and nothing will load, other times the network won't even show up or it will say connection timed out. As far as my xbox is concerned, I forwarded all of the necessary ports and set up a static IP address. If you test the connection it shows that it is connected with all four bars and that the NAT is open, yet none of my friends can hear me talk, and I can only hear them sometimes. This is the most frustrating thing ever, because it appears as if everything is working properly. Cisco claims to be so easy to set up, yet I call their support line and they can't even help me. I have no idea what to do, can somebody help me out