Ok, here we go
Problem is, that whenever your MAC contains A-F the software gets wrong results, when comparing with the stored result in the license file.
here's a workaround:
get a new license file for medusa for a mac address like 002186553423. It's important for you, to obtain an address, that has no A-F in it.
then start a terminal and type
ifconfig eth0 down
ifconfig eth0 hw ether 002186553423
ifconfig eth0 up
now you can start medusa. Note, that you have to do this with the same mac-address ererytime you have started your system new.
P.S. I made an input to the developers of medusa and hope,that they correct this error in the next version. Then we can use our real mac-address