Have you tried unplugging the router for about ten minutes and trying again?
You could also try resetting the router - this will involve r-entering all of the settings.
There may be a problem with the wireless channel of your router - go into the configuration pages and see if changing this channel helps - a lot of routers have a default channel setting of 6 - try 1 or 11.
Are you sure that you are using the correct network key on your devices?
This piece of advice is from a Belkin forum
"f your htc device has WPS(wi-fi protected setup) in the wireless settings enable it with the wireless on, now somewhere on the back of the router should be a small button with a padlock above it hold, that down for 5 seconds and the padlock symbol on the front will flash and then thats it you should be connected. no need to change any complicated settings "
I have to do this with my own livebox - it is called pairing.