impossible to jailbreak

Hi When i was on 4.2.1 i was able to jailbreak and load TV Flash but after a upgrade to 4.3.1 cannot jailbreak ,in ITUNES after i press SHIFT-RESTORE and CLICK on the custom file .itunes pup up a window tllling me that i'm gone retore to 4.2.1 and then i get error (21) or (1600) or (1601 and 1602) i have 3 micro USB ,erase and re-install itunes  nothing work for me ,its not the DFU state cause i can get to DFU easely ,i'm wondering if it because i jailbreak another apple tv for a friend and use the same laptop ? Hope you can help Thank you

Please look over the troubleshooting tips found here.