Can't connect to wireless, please help

I have an Atheros AR5007EG Wireless Network Adapter and Ubee router with the wireless network setup under wireless connections (security-enabled). I also have a separate Dell which connects to the wireless just fine, with no issues. My computer is Acer desktop with Windows Vista. I bought it and registered it in 2009. I have not used it within the previous 2 years, so it has not had all the updates as it should (that's another issue). After I enter the network password, it does not connect to the wireless router. It DOES connect from the internet cable into the computer, however, and the webpages look out-dated (using Firefox) and when it connects to websites, I get a popup that asks whether the certificate should be trusted. Is this an issue with the wireless adapter (not in sync or compatible with the router)? Or is it an issue with updates? Your help is greatly appreciated.