Downloading in Vista

I'm running the RTM version of Vista Ultimate, and in general it's working
on my hardware. I can connect to the web, and can browse to any site. The
problem is in downloading files: The download starts, executes to about 2/3
of the way through, and then it looks like IE7 just stops trying -- the
download ALWAYS times out at that point. I don't think it's the NIC, as
networking works, in general.

Is there something I'm missing that would cause downloads to fail midstream,
on any site? I've tried it ten different times, on ten different sites, and
the behavior is pretty much the same on every site. I try the same sites
using Windows XP, and the download always works fine.

Any thoughts? -- Ken