Might be your sdcard. Backup everything and format it with SDFormatter then copy your files back,if you keep receiving errors about sdcard you could have a faulty sdcard.
You could also backup your data with titanium backup, boot into CWM make a backup of current ROM and make a fresh install of a new ROM, there are stock, CM7 and MIUI as CWM flashable zips for easy install in CWM pick the one you need, flash it and restore your apps with titanium backup (preferably only app not app+data as you're getting databases errors).
Make a backup of your new ROM in CWM once you finish setting it up as you want for precaution. Remove your old backup.
NOTE: If you install CM7 again make sure you have latest build (Internal: Alpha12 | sdcard: Final). Also verify the md5 of the download so you know its not corrupted.
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