How to jb to ics ?? Help needed

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http://forum.xda-developers.com – I am running CM10 alpha 2 and i want to revert of CM9 alpha 13 . I wiped dalvik cache and cache and installed cm9 but the phone is not booting. It stays on boot animation. When i flash cm10 it boots. How to flash cm9 over cm10 ?? ANyway ?? (HowTos)