"Wireless Connectivity Issue"

Hello everyone,
I've recently had a problem with my wireless connection. I've just changed my encryption type from WPA to WEP 64-bit on my router and at that time my PC stopped connecting to the internet via wireless connection.

So, originally I just changed the encryption back to WPA thinking that my adapter wasn't compatible with WEP but, this doesn't seem to be the case.
I am detecting multiple wireless networks around the area however, when trying to connect to one in particular it always comes back with the error message, "Wireless connectivity issue". So, I'm quite sure it's not an adapter issue but, am a bit stuck with what to do next.

I'm using a Belkin F5D9230-4 Wireless Router with 64-bit WEP encryption.

Thanks for your time.