I own an MX700 as well, and it's an excellent game mouse. Many games, however, have the same problem of recognizing the other five buttons as well, but doing this will get around that easily:
Let's say you want to make mouse button 5 to reload your weapon. Go to your mouse settings and find the menu which allows you to assign keyboard buttons to your mouse buttons. Find the option for button 5 and map it to a key of your choice, like PageUp. Apply your settings, open Planetside, and go to your keymapping options. Find your action (in this case "Reload") and map it to the key that you mapped button 5 to (in this case PageUp). Now if you hit PageUp during the game, you'll reload your weapon. But since your mouse 5 button is also effectively PageUp, hitting that will also reload your weapon.
That was just an example, you can map all sorts of functions to the other buttons. Consider upgrading your mouse software if you haven't already. Probably won't make any difference, but better safe than sorry.
Hope that helps.