I do have a Seeedstudio GPRS Shield (SIM 900) mounted on an Arduino Uno R3. When I do follow the “Getting started” section from the wiki page (http://www.seeedstudio.com/wiki/index.php?title=GPRS_Shield_v0.9b#Getting_Started_-_Fun_with_AT_Commands), I do get the following when I am switching on the GPRS shield:
+CPIN: NOT INSERTED
And the NetLight keeps flashing.
SIM card inserted, tried with and without external power.
Does anybody do have an idea of what is going wrong?