When I render one of my reports I receive the error message  “A generic error occurred in GDI+”.

I figured out that one HtmlTextBox receives quite a long HTML from the data source - exceeds 32 768 characters. In my experiments, the error starts appearing if the text is longer than 32 775 chars.

In this case, the Reporting engine shouldn't throw a misleading GDI+ error but instead throw a more specific exception.