I found this post here http://xdaforums.com/showthread.php?t=1644790 that says it might have to do with your SD card. Where are you storing your system files etc? What has changed since you last successfully booted into CWM? Have you tried just re-flashing ClockworkMod through Odin?
You can get the most up to date version on their website and use Caboomi's Recovery img2tar Odin Maker http://xdaforums.com/showthread.php?t=2281287 to convert it from an img file to a tar Odin can read. Works great. Takes less than a minute to do.
More info would be great if that doesn't solve your problem!
Similar threads
