Haven't encountered that error when using Windows XP.
Does this happen with a brand new file?
Does this happen only on certain web sites?
So far, I found only the mentioned website https://www.filemaker-magazin.de and sub pages.
I discovered the problem by accident. I do not know why this webpage and what specific feture on that page will 'break' the data viewer. Without any clue it does not make a lot of sense to start looking for another webpage. Perhaps FileMaker can use some of their tools and look into it.
BTW, it is kind of funny (or sad) that this error occurs with a website, whose main purpose is to promote FileMaker products.
I asked about web sites because a problem like this could be due to problems with your file, or problems with the specific values returned by the web site. If this only happens with a specific web site, that narrows down the possible causes a lot when the one of the FileMaker Techs gets around to responding to this thread.
I can definitely reproduce this and putting the function inside a Show Custom Dialog box produces a number of strange behaviors, but no error messages. (Dialog never appears and then you find you can't close the file. You can use script manager to open the script, you can make sometimes make edits, sometimes not and you can't save the changes if you can make them. While opening the script debugger didn't show the script running, once you have the script editor open, you can open the debugger and halt the script to regain control.)