Hi! Have you looked at the tablet's settings and maybe check things out there? I also work with a Genius tablet and had problems with it not registering itself when it came to drawing on gimp. After making gimp get into full-screen, then unplugging my tablet and plugging back in, it starts to work just fine. Oh and also trying to replace the pen's battery might help.
It's a great tablet, but many times I have to repeat the whole, plug-out & plug-in process to get it working well.
I don't think I really answered your question but I hope this helps in someway!