I also suffer from the "can't update KDE file associations" problem, using konqueror-3.2.3-1. In my case, I'm trying to add an association on .PDF files for /usr/bin/xpdf.
I get this in my .xsession-errors: kbuildsycoca running... Reusing existing ksycoca KURLRequester::setProperty( "mode", value ) failed: property invalid, read-only or does not exist So, it's telling me what's wrong (but I'm not sure how to fix it). cheers, Simon