GPRS Shield v1.0 don´t work!

I have updated the board with (1137B09SIM900M64_ST) this firmware.
But I get not answers to the AT Commands.
The one exception is if the board is in the Init process. At this time I get an OK or ERROR to AT Commands. But after the Init was finished, the board not respond to the AT Commands.
What is the Problem?
Is the board in Sleep Mode?

Sorry for my bad English :laughing:

The Problem was the Power Supply!
I have soldered a 2200µF Capacitor (+ to Vbat and - to GND)
And it works!