This problem usually arises when the network security key type or characters don't not match those stored on your router.
If your router is a DG834GT use a web browser to access the router's configuration by typing 192.168.0.1 in the address bar. I believe the default user name/password are admin/sky (these should be changed to prohibit unauthorised access).
The interface is fairly intuitive and you or a knowledgeable friend should have no probs setting up network name (SSID) and security type and code.
It's easy then to make your network adapter's config match the router's.
I hope I don't seem patronising, but I know some can find it a bit daunting and I have no idea of your experience!
jt
jt
January 2008