Sorry to hear that. It took about 30 minutes for me to play but now seems to be working fine. My first video, however, plays audio only. I've found that videos I make straight from my webcam and do not run through any editing software seem to work just fine. Also, it seems like you need to keep your finished file smaller than 100 MB. This can be pretty difficult to do unless you have a video that's only a few minutes long and/or you want to sacrifice quality.

However, I guess I'd rather have lower quality and have the video play than higher quality and not work at all.

Not to worry, though, I'm positive that the creator(s) are working on fixing everything and probably making progress every day.

I don't think that anybody expected DTube to gain popularity as fast as it did. It seems people were simply clamoring for an alternative to YouTube! This is a great thing!