M1306B restarts every few seconds without appli running

Device restarts all the time, even if no application is started.
That happens on device after I use connection to GPRS for a first time.
So I close application with AT+WOPEN=0
But device still resets all the time. +WIND: 13 means reset.

This is response that I get:

+WIND: 13

+WIND: 1

+WIND: 7

+WIND: 16

+WIND: 13

+WIND: 1

+WIND: 7

+WIND: 16

I don’t know what to do.
I tested 2 sim cards. Both are working fine on other cell phones.
SIM cards are correctly inserted.
For now I did that on 3 devices and all of them resets every 10 seconds.
On 2 of them I tried to restore factory settings with AT+F but this didn’t help.

Device works fine without SIM card!

Does anybody know what might be the problem?

see also: http://www.wavecom.com/modules/movie/scenes/forums/viewtopic.php?t=1410