Dynex Router Problems

I have been trying to get to my router through my internet browser by typing in the default gateway into the URL bar but it won't pull anything up. I have tried all the ip's on the CMD's list thing but none will work. It has worked in the past but for some reason not now. I am trying to get to the ports to open some up for a minecraft server. I have a windows 7 64 bit and a Dynex wireless G router that I haven't really messed with to much. So if any one could try to help it would be appreciated.

You might look at the instruction manual. There might be a reset button that will restore it to a know state from which to start over.