There have been some changes, both on the NING platform, and the YouTube platform that will affect your ability to post videos here.
First and foremost, to post a video in a comment, discussion, blog, or text box you must use the little blue "filmstrip" icon. Look at the photo below, you will see above the actual text editor where it says ADD, then you see, LINK (post links), a PHOTO icon (upload photos from your computer, or paste from a URL), then the blue "filmstrip" icon (embed videos), a paper icon with a T on it (paste text from Word), and then a "paperclip" (upload files).
Now, to add an embedded video, you click on that blue filmstrip icon. A window will pop up asking you to paste the embed code.... BUT YouTube has changed their formatting to what is called iframe. iframe does not work on NING yet. NING is currently working on a global fix, but UNTIL THEN, here is what you do....
Here is a screenshot of what you may see when you embed a video from YouTube. Notice where it's circled? That last checkbox there is what you want to get. That is the old HTML embed code, and that is what you have to use. Not all videos on YouTube have been converted yet, but a good portion of them have been, so when you click on EMBED, look for that list that is circled above.
When you click the filmstrip icon, that window pops up, just past the old embed code in there, and you will see a yellow box show up in your actual text editor. When you publish or send, that video will show up just fine. YOU WILL NOT SEE THE ACTUAL VIDEO until you publish, or send. You'll just see that yellow placeholder box, and it will have the F (Flash) icon in the middle of it.
I hope this helps you. :)