Not sure if anyone has run into this problem, or if there is an answer already posted, so I am posting what worked for me. I didn't see it anywhere else.
I am using the Social theme. I had an issue with YouTube videos not displaying in IE when I embedded them in a Text Widget. I tried a few plugins but none of them worked. I know this is a IE issue but I figured I would post it anyway. Here is what did work.
I went here:
Then I dropped in YouTube's embed code and it generated valid XHTML for me. Worked like a charm. I am a MAC dude so I think IE is the devil, but since so many still remain on the dark side I figured I would throw a line.
Oh and the IE Netrenderer plugin for Firefox was also very useful.