While working with Capybara feature specs and Poltergeist, you may have encountered this error before. You also probably tried bumping up the timeout value to no avail. I found a surprisingly easy fix for this issue - update your Poltergeist gem and update PhantomJS to version 2.0! After I did these two things, most of these errors went away.
If you are still having issues after that, read through this issue and see if a solution there helps.