I noticed the mouse issue too when I reformatted my Macbook Pro and put 10.9 on it. However, I discovered a fix for this. If you log into GW2 and the mouse starts going crazy, just COMMAND+TAB out of Guild Wars and go to the desktop. Use your mouse or trackpad and click and drag anywhere on the desktop (as if you’re making a selection). Then COMMAND+TAB back into Guild Wars and it will be gone. Works every time for me. Try it.