Internet connection is acting wierd

[cloud962]

Okay-im new to these forums and im a computer nub lol. I just got my internet connection fixed because it was acting slower than what it should have been(1 mbs when it should have been 5mbs) and the guy that fixed it gave me a new modem.

(I use a wireless connection BTW, and connecting through a wire is out of the question-sorry)

Ever since i got my internet connection fixed i've been able to download things faster but when i play games such as Combat arms and CoD4 multiplayer online(on my ps3) it keeps getting disconnected/interrupted every 10 seconds or so. When it gets disconnected/interrupted i get teleported back to where i was a couple seconds before-which usually gets me killed.
(in call of duty 4 it says "Connection interrupted" and i my character rewinds to where it was 5-10 seconds before)
(in Combat arms it doesn't say anything and i just get rewinded to where i was 5-10 seconds before)

I'm not running any downloads or anything but my sister might be and theres no way she would stop if i asked her to.

Is there someway i can prioritize my games or anything?
If you have any other solutions can you post them please?

(Im using a linksys wrt54g router and i know its not how fast my internet connection is because before i got it fixed it was 5x slower(around that) and it would never do this to me)

Early thanks ;D

I dont know if it will stop doing this if my sister is offline since she is almost ALWAYS online. ><
Edit: i hope this is the right forum since im talking about CoD4 on my ps3