Are you sure you have allowed custom files to be downloaded (via options)? The red text that comes up at the top basically tells you the lua cache is missing, I am fairly sure. This means that it is not being downloaded.
Do you have CS:S
FULLY downloaded?
By the way, when embedding youtube videos, put the embed code between the tags.
Code:
[youtube][/youtube]
For example the embed code for your video is:
Code:
<object width="640" height="385"><param name="movie" value="http://www.youtube.com/v/4kws7qs87FY&hl=en_US&fs=1"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/4kws7qs87FY&hl=en_US&fs=1" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="640" height="385"></embed></object>
Therefore you do:
Code:
[youtube]<object width="640" height="385"><param name="movie" value="http://www.youtube.com/v/4kws7qs87FY&hl=en_US&fs=1"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/4kws7qs87FY&hl=en_US&fs=1" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="640" height="385"></embed></object>[/youtube]
End result: