The following problems generally mean that
webkit_server has crashed:
QCoreApplication::postEvent: Unexpected null receiver
WebkitInvalidResponseError with "Invalid command"
Errno::EADDRNOTAVAIL: Can't assign requested address
If you encounter one of these errors, please set your driver to to
:webkit_debug and attach all output from your test to the issue. Without this output, we can't do much to fix your issue.
If you happen to be using a mac, your mac console may reveal interesting things if the problems that you are running into have caused thread crashes. You can access this on your mac within the /Applications/Utilities folder as the application "Console". Clear the console display and attempt to reproduce the problem. If your problem is causing threads to crash you should see a crash report within the "User Diagnostic Reports" section in the left hand nav bar after reproducing the problem.