When I found that I couldn’t open previous projects, I headed over to the Deep Zoom Composer Forum to let the team know of this problem. Kirupa was quick to respond to me and I’ve sent him one of the non-opening .dzprj files for investigation, as did others.
As a result there now is a new Deep Zoom Composer release which no longer has this problem, at least not for me. I sure hope you didn’t delete your old project files! Should you still have said problem, please send your non-opening .dzprj files to Kirupa (address can be found in their blog post), so they can look into it.
Besides this improved project support the memory handling has also been improved, the Seadragon Ajax Templates have been updated again and various other tweaks were done.
NOTE: Please uninstall any older versions of Deep Zoom Composer prior to installing this new version.
Don’t forget to check out the updated documentation! It has become a true User Guide with topics ranging from what Deep Zoom is to how to actually use Deep Zoom Composer. You can access the User Guide inside Deep Zoom Composer by going to Help > User Guide or by pressing F1.