XBee still hung even after an hardware reset

Hi everyone
I have a problem with XBee S2

Sometime (often) it hang and cannot communicate with on the serial port.
Even a hardware reset will not bring the communication back.

The only way to get the serial communication back with the arduino is to make a Remote AT command from another xbee device on the network to this xbee.

I use the AltSoftSerial Library and the XBee library.

Does anyone has already experienced this issue ?