Perhaps it was the fault of the interviewer and the way he framed his questions (they were slightly involved questions -- "write a command line utility that converts an image file, include unit tests, etc.)? I would often have to write my code in the online editor... (so the interviewer could observe my "style") and then bounce out of the browser, throw it into iPython or sublimetext, run the code, debug in my editor... go back to the browser... write my updated code out... rinse repeat.
Code interviews are a bit nerve racking to begin with -- and interrupting my workflow so jarringly doesn't really help. I prefer when hiring managers have me branch a git repo on git hub, encourage me to commit my changes to a project frequently and discuss my thought process on the commits. I think that process works better for both sides.