I see that you're running on some sort of Unix. Have you installed Graphviz on your system (the executable should be called dot)? For more information see https://cpas.fhcrc.org/Wiki/home/help/1.5/page.view?name=thirdPartyCode.

After you get this error, does the directory it mentions (/usr/local/tomcat/temp/ExperimentRunGraphs/Folder8/ in this case) exist? Are there any files in it? If the directory does not exist, it may be a problem with file permissions - be sure that the user running the Tomcat process has permission to create directories in the /usr/local/tomcat/temp/ directory.