I have exactly the same problem with my Wildcard TE121.
I'm not a specialist in ISDN technology but what I (at least I think) I know is that it is provided to our company via SHDSL.
The signal seems to be modified by an Adtran 6540 modem that forwards the signal to a G.703 port.
When I connect the card to the modem it flashes red. Neither a straight-through ethernet cable, nor an E1/T1 crossover cable makes any difference.
Also all possible configuration changes (that could be made with FreePBX) in every combination didn't helped.
I'm trying about two weeks now to get this work...
Our previous phone system (which is quite old) works just fine in this structure.
Maybe someone here had the same issues and knows what goes wrong here?
We're using Asterisk 1.8 and the newest version of DAHDI.