I have had this plugin working but recently updated Firefox on the Jenkins box to 33.1.1 (it was 31 I believe) and now all my Selenium tests fail.
It hangs at:
Starting to run selenium builder command
Starting test run.
Error running selenium builder command
Build step 'Invoke Selenium Builder script' marked build as failure
If I can pull log files or something please let me know. I'm going to try and reinstall an older Firefox version to see if it resolves the issue.