Hi Sergio,
Needless to say this is very strange. I think it must be a weird mess with configuration files, but I haven't seen anything similar before.
Please reset the entire PixInsight platform by pressing the Control key while you launch PixInsight Core. This will run PixInsight in uninstall mode, a special management mode that erases the entire PI configuration. Say yes when a dialog box asks you for confirmation (Warning: this will erase all of your Preferences settings, which you'll have to set manually).
Let me know if this cures your issues.