SharePoint 2007 / WSS 3.0 - Fixing the "Unable to Add Selected Web Part" ... "The File is Currently Checked Out" Error

Yesterday, I had to post a YouTube video to our SharePoint WSS 3.0 intranet site. If you're not familiar with embedding a YouTube post into a SharePoint page, your best bet is to use the Content Editor Web Part. However, when I went to add the CEWP today, I was receiving the following error -

Huh? Before that, I also noticed that when I was trying to add the CEWP web part to our home page, I was able to see the content, yet no other user was able to see the same content.

If you're struggling with this error, you'r in luck because the fix is simple. Just open up SharePoint Designer, navigate to the page that is giving you the error, right click on the page and select "Undo Check Out". That's it - once you do that, try to add the CEWP and it should work. Hope this helps!