If you power cycle the router (turn it off and then turn it on again) then wait for it to try to connect, does it successfully connect?
Which make and model wireless router do you have?
Does the wireless adapter work on other networks (free hotspots in your vicinity)?
Is your home network using wireless security? If so, if you temporarily disable the security, can you connect? If you boot to Safe Mode with Network Support, can you connect to your home wireless network? These steps are an attempt to eliminate things that could be causing the problem.
WEP does involve encryption (it is just a weaker variety than WPA). If you are using WEP, then temporarily disable it. Also try disabling the MAC Address filtering. If you isolate the problem to one of these security features, then you can always go back in and set it up again, one at a time, to make sure it still works.