What does a "o" symbol instead of "3G" or "E" mean? [duplicate]
You are connected to GPRS/1xRTT since other network connection types are not available.
iOS 5.1 status icons
On GSM (All but Verizon):
- 3G = UTMS/HSDPA
- E = EDGE
- o = GPRS
On CDMA (Verizon):
- 3G = EV-DO
- E = no equivalent - not possible
- o = 1xRTT
(iPhone User Manual on Page 12)
It means you are using the slower GPRS connection. Probably because there's no 3G/EDGE connection or the signal strength for 3G/EDGE is very weak at your location.
Nothing to do with your jailbreaking.