Yeah it's strange that the icon is not being shown properly in your threadlisting Erwin, did you use an ID number that is shown via PHPMyAdmin - it may not be the same as the icon name - e.g. my iconid 37 corresponds to icon14.gif.
No icon is being set, I guess to solve the broken image at least you can set the iconid to 0 (none will appear). This is what is being shown in your threadlisting
PHP Code:
<img src="" alt="" width="15" height="15" border="0">
Word Wrap Bug
Another thing to note is that you may notice a break occuring somewhere in the middle of the Discuss URL or the Discuss text - you will either have to set your Word Wrap to a large value or else to 0 to stop this.