This is an important issue that the developer will wish to investigate and fix. Send the crash report along with the file that caused the crash and a copy of your description (above) of the steps required to reproduce the problem to Nick Nallick email@hidden.
I do wish that Nick would stop playing about with the file format. Not even version 3 files are compatible between different sub-versions. If this is going to keep happening then we will need a facility to save to a version number, especially once Nick decides not to support 10.4.11 any more.