I am getting this error when I include an opensource library that I had to compile from source. Now, all the suggestions on the web indicate that the code was compiled in o
Did you compile with Eclipse? It uses a different compiler (not javac). That should not result in this error (if everything is configured properly), but you can try to compile it with javac instead.
If that fixed the problem, try to see if Eclipse has some incorrect compiler settings. Specifically have it target Java 5.