I was able to fix my USB. I think this is happened becasue my RT6 is the 1st series, where only a 4G SD card installed. Before the loss of the USB, I have installed the new 2013/14 maps and the last file was failed because of insufficient space... Might be that my SD card was so full that it was not able to cache the MP3 to play (only guessing). So the solution which helped finally:
- Had to use RT6_Mirascript (BIG thanks to mira308sw!!!)
- With RT6_SPY I have removed all "SPY" files (they are log and other files, similar to "temp" folder on your PC)
- Than with RT6_CONFIGFLAG I have switched USB to "1"
- Restarted the RT6 (Mirascript will do anyway)
USB works like charm again.