Firefox hangs with @Push. Vaadin 7.5.1/tomcat-7.0.53

Vaadin 7.5.1, firefox 34.0.5, opensuse-linux, apache-tomcat-7.0.53

with 7.4.5 runs ok.

setPollInterval(1000);

with 7.5.1 runs out of CPU, don’t catch any event, even without use accessSynchronously(new Runnable() { })

I fixit, something I can’t find in the docs, is when you upgrade the Vaadin version, Ivy clean all caches , refresh and resolve must be a mandatory action.
Without this, I have a lot of differents problems, but worst, was that my application can run most of the functions.