disappearing artboards

Hello everyone.

If I make 2 or more artboards in onw file and make some objects  and save. After that if I open the same file 1 or more artboards dissapears moreover if I make 10 or more artboards for presentation after saving them I open and see that a few artboards changed their place.

Example: I made 2 artboards for visit cards 90*50. Saved. OPen and as u see exists only one artboard, but guidlines show that here were two