We can look into this further. Most likely it is some sort of memory problem that we may not be able to fix entirely.
What OS are you running? What version of DW? How much RAM do you have?
The way we would address this would probably be to add an auto-save and restore feature so that if anything happened during applicaiton you could close DW, release the memory, and then start back over from where you were instead of starting over.
I will have our QA team look into it more if you can give us more information about the machine you are running on and how many changes you are making before experiencing a problem.