Can't log in to deployed site

[Jeppe Jespersen]

I have deployed a site that uses Memberships and Roles to a production
server. When I'm logged on to the production server, and i browse my new
site, i can log in to the website with no problems. I can browse the website
from a different machine with no problem, but if I attempt to log in, the
login screen simply posts back without loggin me in.

Any Ideas?

Jeppe Jespersen
Denmark