I think the title says it all really... On hitting the share button, and clicking the Facebook button, instead of getting a thumbnail preview of the relevant video, I get a captcha verification picture.

Strangely, if I post it all the same, and then click it from within Facebook, I get to the video as per normal. And the behaviour is not consistent with ALL videos. For example:
linking to http://www.youtube.com/watch?v=v_8o9b8tg34 gives a captcha thumbnail, but linking to http://www.youtube.com/watch?v=YcFnvULy8zA is giving the expected thumbnail preview.

This is happening with both the short and long link versions in the share options, and is even repeatable if I manually copy and paste the URL into Facebook. Also, MySpace appears unaffected by this bug.

I read on one thread here (which has since been closed to replies of course) that the problem could be solved, as was marked as solved, by simply placing a semi-colon at the end of the URL. This is not working for me however.

Any help would be appreciated!

1) On the YouTube video page, click "Share" – be sure to select "Long Link".
2) Copy the link and paste it into your Notepad program.
   Ex – http://www.youtube.com/watch?v=2AOERUldK0A
3) Add "&sns=fb" to the end of the link.
   Ex – http://www.youtube.com/watch?v=2AOERUldK0A&sns=fb
4) Copy your new link and paste it into your Facebook status.
5) Cross your fingers.

I've found when copying & pasting the address that appending just about anything to the end of the 11-character video id (e.g., the letter "x") will allow the actual thumbnail to appear, rather than the captcha

Spid's worked perfectly. Thanks very much!