Craaaaaaaaaazy Cookies

You want a login to one URL to work for all?
Set $cookie_domain in config.php to  ".dreamsfade.com" (without the quotation marks)
Of course, after you do this make sure to clear all the various cookies you accumulated from the different addresses

Your symptoms sound like a cookie collision. Are you sure you've tried clearing your cookies?

Rickard, Smartys, I went into the firefox preferences menu, selected view cookies, and deleted every cooke for my site one by one.

At present, the only cookie for punbb is as follows:

Name: punbb_cookie
Content:
Domain: .dreamsfade.com
Path: /
Send For: Any Type of Connection
Expires: At end of Session

Okay, I've tried the following, all with failure (deleting my cookies after each attempt):

Login at http://dreamsfade.com/board, logout immediately after login. Failed
Login at http://www.dreamsfade.com/board, logout immediately after login. Failed
Login at http://www.dreamsfade.com/board, navigate to http://dreamsfade.com/board/index.php immediately after login, logout. Failed.
Login at http://dreamsfade.com/board, navigate to http://www.dreamsfade.com/board/index.php immediately after login, logout. Failed.

Here is all of my pertinent information.
$cookie_name = 'punbb_cookie';
$cookie_domain = '.dreamsfade.com';
$cookie_path = '/';
$cookie_secure = 0;
$cookie_seed = '912941e0';

Absolute URL to Board: http://dreamsfade.com/board

Base URL from the Admin->Options page: http://dreamsfade.com/board

Subdomain:
http://board.dreamsfade.com redirects to http://dreamsfade.com/board/
http://www.board.dreamsfade.com redirects to http://dreamsfade.com/board/ (not explicitly set, just seems to work that way.)

Redirects:
http://dreamsfade.com redirects to http://dreamsfade.com/board
http://www.dreamsfade.com redirects to http://www.dreamsfade.com/board (can't find how to change this)

The cookie seems to be the same regardless of whether I login from http://www.dreamsfade.com/board or http://dreamsfade.com/board.

If I've missed any pertinent information, please let me know.

Thanks for your help guys. This is driving me crazy.

Alright, I cleared all private data in Firefox. I logged in. Clicked the logout button, and it worked. Then I logged in again, clicked on a link to a forum, then clicked the logout button, and it didn't work.

There isn't a limited number of login/logouts in a given time period, is there?

Is my path correct?

OK, I found the problem
Your server is sending this

Cache-Control: post-check=0, pre-check=0, max-age=18000
Expires: Thu, 21 Jul 1977 07:30:00 GMT, Thu, 15 Jun 2006 22:13:24 GMT

When PunBB doesn't send max-age and only has the 1977 bit. My problem was fixed when I turned off caching, so that would be the issue