MN700 and Fiber Optic compatibility?

I just purchased a MN820 Kit which includes the MN700
base station and a MN720 wireless card. I have a "modem-
less" connection to DSL via PPoE. I called Microsoft to
help getting it set up and they had it working well when
I hung up. Then I rebooted to ensure it stayed that way
and it didn't. I can not get it to stay connected for
longer than several minutes and the only way I can get it
back on is it reset the device. I have turned off the
802.1x authentication and have tried updating the
firmware but no success. I called Microsoft again and
spoke to another technician whom I had a serious case of
doubt in his skills. After answering the same questions
over and over he popped up saying that fiber optic wasn't
compatible with "Microsoft Broadband Devices" ?????
Seems mighty fishy to me. Does anyone know if this is
true or bullhocky?