I’ve got the same problem!
I am unable to communicate with GPRS shield via terminal program. All jumpers are in right position, SIM-card in place and working (tested on real phone), Arduino connected to USB and external power source. Tried different terminal programs with no luck.
After pressing PWR key on GPRS shield in 20-30 seconds status become red and green “Net” stops blinking. As I understand from other reports this is ok status: network found and connected.
I successfully sent SMS from the shield in Xbee mode. But unable to communicate with the shield in terminal program. I used to own 2400bps modem, so I know how to use terminal programs and comminicate with modems via AT commands quite well.
I have Arduino Duemilanove clone, it works perfectly in all tutorials from Arduino’s site.