Could you tell me what was wrong? I have the same problem here. G400P with 1 SIM card and the gsm show spans always gives me the same thing: "Provisioned, Down, Active". SIM is OK (i'ved test it on a mobile phone). I have already try with another card (G400E) and does the same thing dahdi start doesn't give me any errors.
What version of your chan_extra? How about using latest version chan_extra-1.2.1?
Normally, it would be DOWN if GSM doesn't receive the signal or it doesn't successfully initialize. Can you enable the verbose and debug to a higher value and post your whole call log here?