Ok, I finally got it (even if I don't know the problem itself). What I did is:

1. I reflashed with
RX-51_2009SE_10.2010.13-2.VANILLA_PR_EMMC_MR0_ARM
RX-51_2009SE_20.2010.36-2.003_PR_COMBINED_003_ARM
both from this torrent
(lens not working yet)
2. I installed testing CSSU

Now the lens and headphone jack is working fine and all the stuff (powerkernal, fcam, ...) as well.