cygwin makes shared folders on vista

If I do a mkdir in a bash shell, it creates a folder that vista thinks is shared. Doesn't happen in the normal vista cmd shell. Doesn't happen on XP. And turning off sharing in vista takes forever (minutes).

Worse, if I untar a tgz file, in cmd or bash, it creates a vista shared folder. chmod -R doesn't help, and unsharing in vista again takes forever and doesn't even unshare all the sub folders and files.

Has anyone else seen this behavior? Any idea how to fix it? Could my cygwin installation be bad?

Thanks.