I also experienced that sometimes reconnecting to the GPRS is impossible until WCPU reset, altough i only use GPRS and SMS so the problem is probably not the same. I tried a lot of things to amend the issue but failed. This problem is very rare (1 per month, with lot of travel around GSM networks), and a fast reset is bearable in our application although i am not happy with it.
Anyhow, as the OAT application has more and more role there should be an easy option (or working mode) to turn off/reinit the GSM stack and during the GSM off period the complete WCPU functionality should be available (except the GSM related stuffs). We can think about the wireless fuctionality as a periphery, which we can turn on and off whenever we want. Probably, this functionality could save us from rebooting the WCPU sometimes and could be usuful for special applications.
And one more GPRS related bug which will be hopefully corrected in the coming firmware (or at least a note should be issued how to avoid it):
If somebody experiences a lot of IP context disconnection during roaming ( usually periodically around 15 or 30 minutes), the problem could be a specific SIM toolkit command which could be received from some GSM networks. The SIM toolkit is deactivated on the WCPU by default, with activation ( AT+STSF=1 ) this kind of problem will not occure.