iPhone 4 looses 3G connectivity about 5 minutes after boot whereas 3G icon is still displayed !

Hi,

I have an iPhone 4 with an SFR (French operator) SIM card.

Since Friday my iDevice has had the following behaviour:

- 3G connectivity cannot be used with applications: for example, Safari cannot load a page when 3G is selected (3G icon near my operator name at the top of screen with 5 bars).

- When I reboot my device, the apps can use 3G for about 5 minutes and then 3G connectivity disappears but I STILL have the 3G icon.

- Curiously, if I disable 3G connectivity in "Settings" in order to force EDGE or GPRS then the device still maintains the EDGE/GRPS connectivity (apps can have access to the network). Wifi works also very fine.

Thus my conclusion is that 3G hardware module is OK since this module is the same for 3G/EDGE/GPRS systems (same antenna for the 3 systems) and since I can connect to 3G for at least 5 minutes. I did tge test with the NetSpeed app and I can reach good speeds (of course during 5 minutes max !).

So far, I have not tried with another SIM card. I have tried far away (10 kilometers from my home) and I have the same issue, thus this is not a network bug for a given GSM cell.

I wonder whether I must try a device restoring.

Any idea ? Did you already face the same issue ?

Rgards,

Franz