Post Video from YouTube to Wordpress Self-Hosted Site

There is a new feature which can post youtube video directly to blogger and other blog/site. I tried to setup, and found no problem to add blogger and wordpress.com blog, but I failed to add wordpress self-hosted blog.

I trying to post a video from YouTube to my blog site (dalriada.summerhost.info) , so I have registered my username with Wordpress.com to get an API Key. On the "Add a Blog/Site" page in Youtube and under "Specific Blog Host Requirements", I have entered all the requested information, including my new API Key, but get the following error message:


"An error has occurred. Message: Unknown"

Then I tried other usernames and passwords and even my email address as username according the prompt message, no lucky so far.
Can someone please advise on what my problem could be?