Login Says “Directory Listing Denied”

I have installed and uninstalled 2.7 probably 10 times. Each time I clear out the DB, create another, copy all the files over to the blog directory, hit “install,” get to the Log In screen, type in ID and password and get:

IE7 – 403 error
Moz. FF 3.0.5 – “Directory Listing Denied
This Virtual Directory does not allow contents to be listed.”

This happens over and over. The blog is there, but if I try to Log in from there, I get the same error messages.

Please help – going crazy!