Well... maybe... I have not tested with another rom, mine is A06 from Xda-Developers. But it can be another issues, i. e. about partitioning SD card (if you use ext3 instead of ext1) or maybe a small swap partition... Try to redo everything from the beginning... That's all I can help without touc...
I don't know how is in x51, in x50v is Start->Settings->Mirror and check "Enable Mirror mode"