Hi,
I think I found a bug in my website, this is the scenario: in my page there's a Web Part zone with an editable text inside it. The editable text is not empty but there's some text inserted by the user.
If I decide to hide the whole WebPartZone, when I click on button "Save" I get an "Object reference not set to an instance of an object." error on CMSWebParts\Text\editabletext.ascx.cs at line 794. I confirm that there's no customization of that webpart so it's exactly the original one.
Otherwise if I set the visibility of the editabletext and then the visibility of the webpart zone, then everything works well.

I hope it's clear my explanation and don't hesitate to contact me for further information. If you consider that there's an mistake during the web parts configuration, please don't consider my post.
Thank you.