arg, I found the problem: there was a little little assholewire in the lanjack which connected the 2 wires together...I put a new jack on it and I can now mount owfs perfectly and read the sensors value.
Altough if I run ./OneWire I still get:
for source code and license information
01 03/05/11 11:24:55.323 Opening port: ERR Parameter not found <0xb70356c0>
DEFAULT: owlib.c:LibStart(54) No valid 1-wire buses found
01 03/05/11 11:24:55.328 OW_init error: 22, Invalid argument <0xb70356c0>
01 03/05/11 11:24:55.328 Connect() Failed <0xb70356c0>
I also entered the sensors ID at webadmin to the multilevelsensor, but no value is shown in the orbiter - just the tempsymbol...