haha, This is no problem. You may need the original FLV to re-do it, I'm not sure if it will work with the one that appears to have no picture.
The problem (as I interpret it) is that you did not check the "H.264 Encoding" option. If you move the movie file into iTunes, there should be video, however Finder, Quicktime, and even Front Row will not play it. I believe it will work on the iPod though.
Drag the file back in, and check the "H.264 Encoding" thing, and see if that fixes it. I had a similar problem and figured out that the H.264 is a quicktime codec, and apparently without it, the mac won't play the video. There also appears to be different kinds of H.264 codecs, one is normal, the other is designed more for ipod, which is probably what it did.