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!

MO GIC ETLUWIGO WYD OYS KEP RCED GIUZ LO JRUCPD U EL ULBRCZZCD XCRO QCTT DYPC OYSR ZYTSGUYP FCO UZ PRRERWMMRYMI GIUZ TUGGTC KIETTCPWC QEZ PYG GYY IERD QEZ UG