I have two processes writing to the same log file. <prudent> mode is set.
On one occasion, the two processes simply stopped working, and only
mv'ing the logfile, and restarting the processes so that the log file was freshly
created allowed them to continue working.

Another time, two processes were on different machines. Machine 1 went down hard.
But on coming back up and restarting the process, it refused to work. The only solution
was to again 'mv' the logfile and restart the two processes to create the logfile anew. That is,
simply killing and restarting one of the processes did not solve the problem, only removing
the old logfile did the trick.

I do not know how to reliably reproduce this. I did notice the FindBugs 2.0.0 thinks there
are 4 potential synch problems when I analyzed the 1.0.1 jars for logback-core and logback-classic
together.