Well, I checked it. It was one of the components of the website
engine that caused the error message and the garbage screen. Disabling this component improved things a bit, however pdf making in Joomla (our website
engine) is still full of bugs, it cannot handle tables and illustrations nicely. I tried it with other articles and got the same.
So as an end result I switched off the pdf button (it was erroneous anyway) so it is not possible to create pdf's from now on.
Don't panic though!
If you use the "print" icon, it creates a simple, printable version of the article in a separate window, which you can right-click-save-as at your leisure (and you can print it of course). If you save it as a html document, you can create a pdf from it later by using your own tools.
I hope this helped a bit.
