I recently was able to pin down an error in the software that can clobber some files if you cancel out of a save dialog. I've informed Ziefrank how to duplicate this and I'm sure a fix will be forthcoming.
Likely a file became corrupted, either a player db, your league config, or the draft log. You can try downloading the latest player dbs to rule out the first. Try starting a new draft with the league file you've created. If that goes well, it's likely your draft log, and you've probably lost it. If you want to send the draft log to me (PM me and I'll get you my e-mail address) I'll look at it for you.