Unable to open PDFs in KPDF

After installing the latest Adobe Reader directly from Adobe's site (I quickly uninstalled the version from Medibuntu again that I blogged about before, because I couldn't choose a german locale), I noticed I couldn't open my PDFs in KPDF anymore. I found some errors from AppArmor in /etc/messages, but according to Google they were not relevant. Than I found a post describing the same behaviour, noting that starting KPDF as root worked. I checked it, same with me.

When starting KPDF from the commandline, a warning is shown:

kpdf: WARNING: Unknown mimetype 'application/x-kdeuser1'.

This hints at the solution: Adobe Reader installation obviously messed up mime types, going to Konqueror -> Settings -> Configure Konqueror -> File Associations -> Known Types -> applications and deleting user x-kdeuser1 (I also had x-kdeuser2) solved the problem.