Two different apps I am developing at present are running just fine on 3rd Edition testing devices in Russia (N81-bought in the UK, 6290, N78 - bought in Russia), but these apps are not running on E63 or 6290 - bought in South Africa in one case, and in the other case - on two 3rd Editon testing devices bought in Norway.

Both apps are runnig on and not running on

3 devices in Russia 2 devices in South Africa and
2 devices in Norway.

All the devices are 3rd Edition Symbian.

What could be the reason for this? Network opertors (carriers)? Sim cards? Differences in hardware in phones produced for different countries?

Both apps in question deal with call recording/audio playback in the converstaion. (into the GSM line)

I really appreciate any advice on this.