Dear experts,

I am creating my first Concrete5 project, and I have a problem:

Whenever I want to save any modified 'Content' block, I get the following error:

<See attachment>

There is more, but I figured this would be enough.

If I close the window without saving the content, the block (with content) will be duplicated.

I have tried using two different browsers (IE8 and Chrome), with no change in luck.

Thanks in advance