Commented Unassigned: An exception occurred while invoking executor 'executor://chutzpah-js/': Unable to find headless browser: phantomjs.exe [242]

I have the following error message :
An exception occurred while invoking executor 'executor://chutzpah-js/': Unable to find headless browser: phantomjs.exe

This occurs when I start a build with Chutzpah test runner from TFS2013.

If I restart the build controller, it seems to works again.

Comments: How long does it work until it errors again?