Just downloaded MU 1.5.1 a little while ago, and I can't log in after the installation completes. I've tried it with both the subdomain and the subdirectory option, in case that was the problem, but in both cases I'm endlessly redirected to the login page. I've tried having it email me a new password, but the email is never sent. I've also tried overwriting the admin user's password in the database with the MD-5 option on, as I've done with standard WP blogs in the past, but that didn't work either.
I'm developing this site locally, and have done dozens of standard WP installs without a hitch, but this is my first attempt with MU. If it matters, I'm using name-based virtual hosts, such that I just type http://mydomain/ into my browser.
Would hugely appreciate any guidance!