Sharing a folder is extremely slow

I'm finding that when sharing even a very small folder with a couple of items
in it, the "Sharing items..." progress bar is there for about 10 minutes
while the disk thrashes. I've tried on another Vista machine and it takes
about 15 seconds. I've checked without any kind of AV or other resident file
programs running.

What I've noticed is that in Reliability and Performance Monitor, System and
explorer.exe seem to be rifling through all the files in my user folder while
it's setting up the share, and I have a lot of small files from SDKs with
source and documentation. Could there be a bug that makes it check all my
files??

Does anybody else get this slowness?

Sharing in XP on the same machine was a lot faster, or was at least
proportional to the number of files being shared.