Simultaneous PS3 and 'net connection probs.

I have recently purchased a zyxel P660HW router. The main reason for purchase being that my son could play online on his ps3 which is in a different part of the house to the computer. the router works fine when accessing the internet (although downloads seem a lot slower than when through the previous modem). The problem is that when I then turn on the PS3 the device does not detect its presence unless I restart the computer and restart or reset the router. Once I have done this it then plays online fine. Then when I try to access the internet on my PC it gives me a 703 error unable to connect. then I have to restart my pc and reset router to access the net again, then the bleeding PS3 won't play online and so on. Please help. I have spoken to other people who can play online games fine and access the net at the same time. I have rung numerous different 'help' desks which have cost a small fortune, none of which have helped me with the problem. The last one I rang was Currys where I purchased the thing from who said there was something wrong with the router. So I took it back and exchanged the thing to no avail. Same problem exists.