Today I updated the Firmware, Wifi Server and Web Interface to 1.19 and AJAX problems started. The board could only stay connected for like 10 seconds. Luckily I was able to fix it. What worked for me was changing the Wifi transmission channel of the router to "1" (it was set to "automatic"). If you don't know which channel to use, then download this program:
http://www.nirsoft.net/utils/wifi_information_view.html
It's a free tool and you don't need to install it. Once you launch it, it will scan the wireless networks in your area and display a lot of info about them. Locate the Channel header, and click it to sort by Wi-Fi channel. Switch to the less crowded one. 1, 6 and 11 are the most frequently used.
Hope it helps.
EDIT: oh… you tried this already =(
