Thank you for sending us the error information. We aim to make ArmA2 as stable as possible.
The game crashed due to an attempt to load a save file saved in 1.04 or older ArmA2 version. It is impossible to use your old saves from 1.04 ArmA2 version in the patched 1.05 version. To avoid the crash you have to restart the mission from the beginning (or delete the Save file which has caused the crash from your "Documents\ArmA 2" directory.
We apologize for your inconvenience and we are working on fixing this issue.