kebien, I tested this emmkey on the pc with dvbdream and poweremu2.7 and it opened normally, then I got the emu powervu emc and I played the softcam of the dm800 and also opened, thus indicating that it is a valid emm. The problem must be in some oscan configuration.
You also have a rejected reader,so,the problem can be there.
See if linuxsatsupport reader is enabled and check config.If is the only reader,create one for powervu and test it