 <p>The problem actually was with the Modernizr script: apparently sometime between now and when I first started using it, the Modernizr folks made the getusermedia portions of their code non-core, and thus was not included in their standard download. </p> <p>I'm not sure whether this was the original problem, or whether my downloading the newest version of Modernizr created another problem on top of the original, but removing Modernizr from the equation solved the issue. I now have a working webcam stream again - albeit only in Chrome. I'll worry about cross-platform stuff later.</p>