I'm having the same problem, its accepting my username and password, but takes me back to the log in screen. I'm using both firefox and safari (on a mac) and have cleared the cache and cookies, but still won't work.

I'm using the latest version of opn, downloaded today on a php/mysql database with my host - what am i doing wrong?

I'm having this problem. It is addressed in this thread but not resolved.

To summarize:
-New to OPN
-Just installed
-PHP 5.2.9
-MySQL 5.0.77
-Points to a login page at mydomain/html/index.php
-Nothing to do, nowhere to go from there.
-Can't find admin page
-Tried pointing to mydomain/html/admin.php but it redirects to same page above.

TIA for your help.

Absolutely not. If the extension is .php, even if the user wndoloads it, Apache will process the code, so the user only sees what is processed, not the code itself which contains sensitive information.

And I thought I was the sensible one. Thanks for settnig me straight.