I would simply do what I do on my mobile devices when they refuse to connect to a known network.
1. Delete the Connection in the TV menu. Then, set up he home WiFi connection again to as if it were new.
This fixed my wifi connection issue
If that doesn't work...
2. Delete the cache using the remote control and try again after.
Delete the cache :
Press the HOME button 5 times, the UP button 1 time, the REWIND button 2 times and the FAST FORWARD button 2 times. The TV will reboot twice.