When viewing some Youtube.com hosted videos, you may see the above error a few seconds after playback begins. This is caused by their detection of the sound device and the absence of a sound card on our virtual devices. We are looking at adding adding a virtual sound card to get around this issue. As a workaround until then, you can go to https://www.youtube.com/html5 and enable the HTML5 player. This will generally allow the video to play even without the sound device present.
CrossBrowserTesting Support » Frequently Asked Questions » Testing » “An error occurred, please try again later” error when testing Youtube hosted videos.