Dont know about the button on the adapter...
Are you using the adapters networking software or did you just install drivers and going to have XP handle the details? For a stripped OS (or winFLP) I found that running the utility was necessary for anything past WEP encryption.
Does the utility see the UVERSE wireless SSID? Or it never gets to that point?
Make sure and change the default login info and SSID of the uverse router as well if you have not already.
IF you do not see the SSID of the router I would assume the problem is with the router.
The network key is listed on hte side of the router on a sticker, if you want to changeit... use this link on a hardwired computer
http://192.168.1.254/xslt?PAGE=C_2_1
I have wireless N300 in my house. It sucks.. I am sticking to gigabit ethernet