Paolo, if you have ever uploaded your site to the internet you will have a backup in the backup directory inside the project directory. With WX5 not running, copy the backup up to the project directory, rename project.iwprj2 as project-broken.iwprj2 and thern rename the backup as project.iwprj2, now restart wx5 and try again.

If this still fails and you do not have access to an iwzip file, then I am afraid you will need to start the project again.

When working in WX5 please make regular use of the step5 export, export project option (this will create an iwzip file), these files can be renamed to keep multiple versions, or copied to external media for safe keeping.

I am just starting a new project that is why I haven't uploaded it to the internet.  So that means I cannot retrieve what I already started if it isn't uploaded to the internet?

Paolo, by all means check the backup directory inside the project folder. If a backup exists then try using that. My understanding is that (in Evo) a backup is created on first preview and then only whenever the site is uploaded.

Please make frequent use of export project as detailed above. Whenever I create one I modify the name using Windows Explorer eg myproject01.iwzip so I have a number of backups if needed.