Are you trying to open a project with the xml extension in BAS? Probably your project is damaged, you did not edit it manually using text editors? Try to restore it from backups located here:
C:\Users\User\AppData\Roaming\BrowserAutomationStudio\projectbackups
@GaG Okay thank you for the info. Sounds great and saves work, I'm more and more convinced by BAS. Let's look what the future and the new version will bring :)