The number of threads, http sessions and memory is increasing so much, the application will stop working in time / crash.
There where a lot of messages in the log:

Nov 7, 2012 7:08:46 AM org.kohsuke.stapler.compression.CompressionFilter reportException
WARNING: Untrapped servlet exception
javax.servlet.ServletException: org.apache.commons.jelly.JellyTagException: jar:file:/C:/Tools/Jenkins/war/WEB-INF/lib/jenkins-core-1.466.2.jar!/lib/hudson/executors.jelly:126:26: <j:otherwise> Failed to write to client

Some information about:

• The increase in threads (20121108_ActiveThreads.png)
• The increase in http sessions (20121108_httpSessions.png)
• The Threaddump from jenkins (20121108_Threaddump.txt)
• An analysis about the threaddump (Heapdump data.htm)

Can be found here