lordadb, Thanks for trying to help me! 
Yes, I tried change properties “copy file in working directory”, result is the same crash. But something is start clearing up after a few hours of the hard searching. When the option “automatic hitpoint detection” is turned OFF - Cubase works without this crash! But, I find strange that you do not have “You should save the project now!” alert, because it must be. 
You just can open the Operation Manual PDF for Cubase 7.5, and there on page 390 (The Pool) you will see this:
This implies, that this “You should save the project now!” alert is must be there, but nothing is happened in your case after minimizing. Strange behavior, is bug-like.