I had the same problem in Eclipse. But then I realized I have manually added jfxrt.jar to my build path because I can't get it working with Maven.
I updated the jar in my project, and its working now
Thanks for your reply, however, I had already removed the dependency on my locally installed javafx runtime. I'm still leaning toward it being a problem with the zenjava maven plugin. I will try to contact the author for more information.
I found a solution to my problems here: http://blog.maurus.be/2012/12/02/javafx-and-maven/
By changing my pom to point at the local jfxrt.jar file instead of the one that was in the com.oracle repository, I was able to build apps that I can run stand-alone and against older version of the java jre. But then I couldn't run inside of netbeans, so the link above gives information on how to fix that problem. It has to do with exec-maven-plugin omits adding the system-scope dependencies to the classpath. Adding the location of the jfxrt.jar file to the bootclasspath. Hopefully this will help others who are suddenly facing the same problem.
I'd still encourage you to follow up with the zenjava plugin owner. The zenjava plugin is quite popular and if it doesn't work for later JavaFX versions, it should be fixed.