Same issue here with beta 11. After the first time it happened I thought I had some bad sectors as i had some recent crashes. After fsck'ing same problem. Checking permissions in .canola did not reveal any issues. I fixed it by renaming the canola.db file
and allowing canola to create a new one (first startup hung, killing restarting canola made it happy after removing the db file). It worked again for about a week and then had the same error. Removing the db file fixes it for me but obviously you loose all our podcast settings, etc.

Love canola, hope this can be squashed soon.