I found. Under RHEL (and maybe fedora and CentOS?), by default, the Security Manager doesn't allow the access to classes with a restricted user (like me here, I don't execute tomcat with root).
1) I activated the security debug by this command:
export CATALINA_OPTS=-Djava.security.debug=access,failure
2)I found an AccessControLException
3) I uncommented this lines into the catalina.policy file:
grant codeBase "file:${catalina.home}/webapps/petals-view-ui/WEB-INF/classes/-" {
};
4)I restarted tomcat
So we can close this track by RESOLVED. If you're agree with me, I can add a part into the installation document into the Wiki 
I can't reproduce your problem.
I tested with the latest Petals View on the repository and the last WebConsole in tomcat-6.0.29 and I have no worries of deployment.
Is the problem still persist?