I have the same problem, I have tried in both Mac and PC, also manual install via ssh.
After several hours and im quite good at this I conclude that the unit has not been jailbroken, It seems that although manually choosing the file in itunes and uploading the file has not functioned.
I conclude as others do that the script to compile this file is faulty, itunes most certainly does not autoload the file.
Tethered boot functions but whats the point if its not jailbroken.
I appreciate this is a beta, but had hoped to get some basic functios.
Some seem to have had luck but I conclude that the jailbreak does not function, any ideas?