You can see if it's a GUI bug by using gconftool-2 from a command line. Save the network with the 63 byte key and then edit the settings at the commandline. You can start by examining the current stuff.

gconftool-2 -R /system/osso/connectivity/IAP/

It will take some playing, but you should be able to add the last digit to the key and then see if it will connect.