Yes this happens to me too. I don't know what it is but its really annoying... especially when you're waiting for that item to download and you realise its gonna take longer than ever.

That happened to me loads of times..I was downloading a film and it reached 93% then went down to like 12% then reached 96% and went down to 75% then reached 99% and stopped and wouldn't download anymore.

Really frustrating!