a cryptogram is a substitution cypher in which one letter stands for another. If you think that X equals O, it wll equal O throughout the puzzle. If you need a clue, email me...
RSB QUQ JSH MSUMHP MFTCC JSH FTOQ?
JT AHJ OROB NFTX JSH ETJ TN GTUIUPA ROJHF.
(I'll post the answer tomorrow in the comments)