Fox On Fire
I submitted a gripe before seeing this.
I also had the same problem, then tried uploading with IE and succeeded.
The thing is, I just got back from being gone for a couple of weeks and uploading podcasts with Firefox worked fine before I left.
I'm still using Firefox 1.0.7 as before, so I'm not sure what's different on this end that would cause the problem.
I strongly prefer Firefox over IE, so I'm hoping this mysterious ailment will be cured soon.
Until then, I suppose being able to upload via IE is better than nothing, though I hope it's not the start of a trend.