I'm happy to hear that you've finally got it working (
), but I don't think your reasoning is on the mark.
Your "I cannot forget my password" has (too late in the game) gotten me thinking that after you created your first disk image and stored its password in your keychain you likely created all of your subsequent images with the
same name
and password, so regardless of whether you checked the "Remember..." box or not, they got opened by that original entry; you've apparently deleted the offending item from your keychain, though, and thereby solved your problem.
It's been quite a trip, but all's well...
