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!

RG UHL WIYDMHUG MAS GAJ KWT XLWS UHDN YG OXDLTS D WY DYBXLNNLS PLXG ELII SATL GAJX NAIJUDAT ZLG DN TXXWXMRRXARH UHDN IDUUIL KHWIILTML EWN TAU UAA HWXS EWN DU