I had hoped I had removed this error yesterday, but it seems its still in the code. Also my own setup has the same problem.
I noticed that when the error occurs the next run of jSunnyreports will continue normally.
I have modified parts of the code so it will give more information about this error, and will actually log it into the logfiles. If you have this error and want to help me, please e-mail me and I will send you a modified copy of jsunnyreports.jar