Editor freezes on particular word in particular context

This has to be one of the weirdest problems I've ever ran into, but it's a serious one nonetheless. Last year I installed FCKeditor on one of my clients websites. Everything worked fine ... client was more then gratefull for the added functionality / usability that FCKeditor provided. Two weeks ago however he mailed that the editor failed to process a particular text. First thing I could think of, was there might be some kind of freak character in the text, causing problems. There wasn't. So I began eliminating text and resubmitting x number of times. In the end it turned out that the word "posters" in a specific paragraph was causing trouble. If I deleted it, the text was accepted. If not, the editor would just sit there and do nothing ... or my browser would simply show a "connection reset etc." page after a while.

At that point I thought it could have been some kind of bug that had been fixed ever since ... the site was still running a somewhat older version of the editor.

That being said, I developed a new CMS-backend for another customer a few weeks back. Again FCKeditor was the editor of choice and again it worked flawlessly. However, earlier today one of the site's editor mails me a particular text he had written wasn't being processed at all. I asked him to mail me the text, so I could have a look at it. Before I even managed to do that, he let me know he had been digging around himself and found out the origin of the problem was the word "postergallerijen" (it's not an english text so ...) in his text.

I refuse to believe that a single word could cause such problems ... but I'm clueless as to what could be the source of the problem. Especially given the fact that 2 totally independent sources, on different servers, with different versions of FCKeditor are reporting this problem.

Anyone have any brilliant ideas as to how this could be fixed and even more importantly: why this is happening ?

Thanks in advance.