Can't open the database

I've created a new database and I have imported a table from another one. This table has no formulas, only text and number data.

If I close the database and enter again, all works fine.

I then add a newly created table, with a few fields. One of this fields is a dynamic choice field pointing at the imported table. I've done this operation a few times before and never experienced any problem.

Still, If I now close the database and try to enter again, I get the message shown in the screenshot.

This happened for the 4th time in a row and I don't have a clue why....

Could someone please help?