Chantal Cerboni 

It sounds as though something happened to your package.  Did this error appear when you tried to open the package (the *.sdlppx file) the first time?  Or did it happen after the project was created and you tried to open the project to work on it?  There are a few KB articles available on this topic, perhaps try and check them to see if one fits your scenario?

Hii Paul ,
thank you for your prompt reply. I have finally identified the issue: on my new PC, they had installed Norton AV by default, without telling me. And I had installed McAfee, which is the AV I have always used. So I have uninstalled Norton, and everything works now. But I have not precisely found out if the issue was caused by Norton or by a potential conflict between both AV programs...

Thanks for coming back and confirming Chantal Cerboni .  That's a useful bit of information that might help someone else in the future.

Thanks for coming back and confirming Chantal Cerboni .  That's a useful bit of information that might help someone else in the future.