Thanks for the suggestion, I can see how it would be useful to have such a forum.
This is a known issue and is caused by an update on Mac )to QuickTime if I'm not mistaken). The problem it introduced was that Dreamweaver would believe that certain small images ( such as 3x3) were missing, when in fact they are present. I'm not sure if rolling back the update will help.
Check your order history page for any updated version to the products you have that has been released to fix this particular issue.