Oh dear, I guess you have cracked the two caesar cryptos...
This one is more difficult. Although a simple substitution is easily cracked...
Again the characters are limited to A-Z... But I think I can come up with a 256 version again.

Enjoy!

BX IQO SVKCMQIX MNW XNU GSZ LOSW IQCA KX TLCOZW C SK CKJLOAAOW DOLX EOVV WNZO XNUL ANVUICNZ FOX CA ZLLSLMBBLNBQ IQCA VCIIVO GQSVVOZMO ESA ZNI INN QSLW ESA CI