I asked for it: never, ever upgrade something without really testing it. As mentioned before I upgraded from RC1 to RC3, but I have never taken the time to make sure that the customized plugins I use are also known to the new version. In my case this concerned the fortune and the Google plugin.

So now I have created a personal plugin directory as part of the website generated by NanoBlogger and adjusted my local blog.conf so that NanoBlogger sees this directory.