I recently had trouble connecting a Vizio E500I-AI television to a WIFI network. Even though it stated that is supported WPA2 it would not connect to the router in question with WPA2. Instead, the router had to be switched to WPA/WPA2 (allowing the older protocol which is less secure). In this specific case, the WIFI signal was full strength which can also be an issue with many WIFI enabled televisions.
I'm not sure if the issue with WPA2 was with the router or the TV, but enabling both standards allowed the TV to connect.