1. Please let us know what lecture is giving you troubles. Include the name of the class, the name of the speaker, and the url if possible.
2. Please tell us what browser (including version) and operating system (including version) are you using. For example, Chrome on Mac OSX 10.7, or Internet Explorer on Windows 7.
3. Go to speedtest.net and click on the arrow beneath "Begin Test." If your download speed is too slow (below 4 Mbps), our server will sometimes "time out" before the download is complete.