download goes from 98% to 0%

Hi,
I have had problems with some downloads, for example at one time it is showing 98% complete then it goes back to 0% or sometimes just drops back a couple of %. Why does it do this?

That'll be b/c it detects there's some data missing or not matching up when it initially downlded the hash tree. So what it does is try up to 6 times to redownld that the missing bit(s). It may be due to transfer problems (data loss), or a corrupt file at the source, or the original source has had its info changed for some reason.

thanks for that.