I described the problem and solution here:
I started with Firmware Version 1.0 with probs.
I switched to RPC-Firmware Version 1.01 (still probs).
I flashed the original firmware 1.01 downloaded from the board and everything is OK.
Has it something to do with CPRM? I remind me that CPRM was disabled in the RPC -Version. In original 1.01 is it enabled. (????)