Fixing Panasonic LUMIX Wifi - "Connection to Access Point Failed"

This error occurred to me with a Fritz Box as access point and WPA/WPA2 mixed mode. The first time the camera still connected, later attempts failed. After switching the network mode to WPA2 only, it worked again.

Update: I've upgraded to Firmware v. 1.1 and the issue disappeared.

Otherwise you can probably try resetting the camera settings. Good luck!