Am I uploading my video to youtube wrong?

I just finished making a short clip to test my voicework for my upcoming project, and I was going to have my partner listen to it to decide if we need a new voice actor, but the problem is that it pops up "an unknown error has occured" when I try to press the upload on. I am running WMM on Windows Vista. I have gone to "Publish" twice, and I'm sure it is in the format WMV because when I press the on it shows up WT10.WMV. So what could be the problem here?