Internet connectivity issues.

Hello. My name is Justin, I am having an issue with my wireless internet. on March 12 i bought (mobo, CPU, PSU, video card, wirless adapter, and a hardrive and dvd drive) built the computer. Then a day or 2 ago. we bought a second desktop for the living room (ran with ethernet cord to router).So now in this house we are running "PS3, 1 wireless desktop (custom build), a tablet, a laptop, and a hardwired desktop.

What is going on is. when i have the wirless desktop, ps3, and tablet all connected. everything seems to be fine. if someone gets on the wired desktop. i have to shut off my PS3 to keep internet on my custom built PC. The PC shows i'm connected. But when i open firefox or IE the loding bar just spin (firefox) and barely moves in IE. If i reset the IE advanced options and restart the computer everything seems fine as long as i leave the laptop and PS3 off (no power).

So im wondering why does my browsers not load if these three devices are connected (acer desktop, custon desktop, and PS3). i tend to not use the laptop at all so thats not a problem keeping that off. But just seems weird that 3 devices are effecting Xfinity internet that way.

P.S the Acer is hardwired to the router again and it always works just fine