I am having the same problem, but it doesn't matter what computer I try to log in from. It always returns me to the login page without displaying any errors. My scripts can log into mySQL just fine with the same credentials I supplied on the login page.
EDIT: I realized I hadn't tried logging in to phpMyAdmin from the server itself. The server I'm having trouble with is really a desktop machine I use for a POS application. I opened Firefox on the machine and successfully logged into phpMyAdmin. Something is preventing me from logging in from other computers.
ANOTHER EDIT: The answer to my problem was so obvious I missed it. It's been my week for that. 🙂 My MySQL account no longer had priveledges from any host. It was restricted to the local machine only. Check your priveledges, basil.
Chris