It turned out that the sporadic access was because I had the router set to automatically determine a channel. The T-Mobile WiFi/UMA service will only work with channels 1,6, or 11, which I why it connected to my neighbor’s router (channel 6). Here are all of the settings that you can apply to the router to make it function similarly to the T-Mobile branded LinkSys router.
|Wireless Channel (try in this order)||11, 6, 1|
|For a secure network||WPA 2 is preferred over WEP|
I hope this helps solve some of your problems and that T-Mobile documents this somewhere.