Please describe your setup in more detail. Do you have an OBi110? If so, is your landline connected to the Line port? Any phones connected directly to the landline (as opposed to the OBi's Phone port)?
Can you call your daughter-in-law's cell phone ok from Gmail? When you attempt to call from the phone connected to your OBi, what does the OBi's Call History show (what service was used to make the call, is the number in the correct format, i.e. 11 digits for GV)?