Since you said on the other comment that you are running within tomcat, maybe one of the following are happening:

* The war is not being generated with the jcaptcha jar (quite possible)
* The web.xml template for jetty and tomcat are different (Which I doubt) and I've only modified the template for jetty. The result would be that jcaptcha servlet wouldn't be mapped and so, no image at all.
* Something else that I currently have no clue.

I just wanna finish the configuration system refactoring and the access control for each snip which probably will be ready by next week and then I'll issue tomcat 's war problems.