Thanks for the replies
Here's some info on my set up and what I've done so far...
I have two laptops that I use wifi with my router, which is set up with "WPA2" security. The laptops connect ok where I have put the PS3. This whole network thing was set up for me but I've figured out enough to enter the SSID and WPA key manually into the PS3.
I've been into the router using the 192.168.1.1 address (got that from the router manual) but I'm not sure why that would help
With my new laptop I just entered the SSID and WPA key in and bingo it connected.
What happens is that when I go through the basic options on the PS3 and then try to connect it flashes "exchanging key" and then comes up with an error message something like "exchange timed out" and by the IP Address it says "failed".
I haven't tried to connect the PS directly to the router, I'm not sure I can - the router is on a different floor of my apartment to the tv.
Thanks for your help.
Claire