Re: installation problem, no theme or login!
Looks like you’re working on it? There is nothing at /forum right now.
Usually when you have no theme, it’s due to a path problem in your configuration. If you look at the source of a page that is displayed with no style, check the path to the style.css and see if that URL is actually valid and a stylesheet is actually present there.
If you can’t log in, we need more information. I would start with no permalinks, rather than slugs or true, to be sure that the forum works. Then set up permalinks with your .htaccess file. Start simple and work your way up.