If you're having problems either getting your video to link or getting your thumbnail to display, try using the link, rather than the embed code. Doing this has solved most upload problems on the site so far...however you might also find this info useful:
Vimeo - use the URL as described above.
Google Video, we've found you need to link from google.com. Linking from google.co.uk is often problematic.
MySpace. Don't use MySpace unless you don't have your videos anywhere else. It's nearly always problematic and we can pretty much guarantee your thumbnail won't load. If you have to and you're having problems: Make sure you're using the URL they generate for linking your video, not the one you can see in the browser bar which is sometimes different.It should start something like this: vids.myspace.com etc
You may get an incorrect error message if you try to view in preview. If you do, ignore it and go ahead with the link.
http://www.youtube.com/watch?v=8PxQKBU0nPg