Network problem

Hello,
i have a linksys wrt54g2v1 router, i have 3 computers, 2 of which work fine,the 3rd one i just got,keeps going from 54 bps to 48,36,and finally drops off, if I use the on and off switch,for internet, it will eventually reset back to 54 bps, I am on brighthouse,on a hp dv9005us notebook
Regards