Modbus read error "break condition"

Hello,
I have the following:
- Schneider SEPAM S42 protection relay
- Schneider RS232/485 converter "ACE909-2"
- Schneider ACE949-2 modbus interface
- my laptop with serial interface and modbus poll software.

I worked fine at the modbus poll simulator for few days i can read and write and everthing working normally and funny.
today, i tried to read frim the SEPAM but i got read error: break condition and write error: break condition.
i tried to troubleshoot the problem but failed.
any ideas?

Thanks