Approving not yet installed module gives SQL fatal error

Once installed, I've gone to "Configuration > Modules", and I tried 2 things:

• if I select one of the not installed module clicking the checkbox,
  and then I click on "Activate" toolbar button, I have an sql error message on top of toolbar:

Fatal Error: Query method is called in class kDBItem for prefix mod in "...\core\kernel\db\dbitem.php" on line 1259