Staic IP Address (and problems with opening ports)

So I recently tried out static IP addressing, which has been a smooth experience with my internet and online games. But on more than one occasion, my IP address would change all on its own, forcing me to retype the IP information in my PC, PS2, etc.

What's worse, with the recent IP change, I can't access my setup menu (where you type your IP address in the web browser). It asks for a name and password, but what I used before (admin) doesn't work. How do I find out the new name and password, or how do I bypass that entirely?

I need to open up some ports to play PSU, but I can't do it without accessing the setup menu. Please help me as soon as possible. Thanks.

Jam it back in, in the dark.