IS this a common problem for X-Keys Pro or do I have a bad one?

I got my X-Keys Pro (USB) on Wed. and twice now the keys on the right and left have stopped working. The center keys and those along the top are fine, but the others don't do anything. The only thing that worked last time was uninstalling MacroWorks and reinstalling it. I've got it keyed in to my WoW macros so I'd rather not have to keep doing that.

Is this common or do i have a bad product?

And if I do and have to return it, should I stick with USB or get a PS/2? While my USB one was in the mail, I read all kinds of posts recommending the PS/2 instead. What's the difference and does it make that much difference?

Currently I'm playing 2 accounts on 1 pc/1 monitor. I will be upgrading my gear in the coming months.

Thanks for any advice.

are any of the buttons on the xkey mapped to anything on the num pad? If they are everytime you hit numlock to autorun it toggles numlock and you lose those keys till you hit it again.
That is what was causing mine to do the same thing.