The quicksearch box in the top right corner does not give any search hits anymore.
The first test was with JSPWiki version 2.9.1-svn-30.
To make sure that JSONRPCBridge was not screwed up by the patch for JSPWIKI-659 I deployed JSPWiki v2.9.1-svn-16 and reran the test.
Still the problem persists.
I remembered I recently upgraded tomcat to the latest release 7.0.37, so I decided to backout to my previous tomcat version (7.0.17).
And guess what, quicksearch works again.
I will dig into the tomcat changelog to see if I can find a possible cause.