Kinesis Spacebar Difficulties

My mother has some difficulties with using a computer, mostly neck and shoulder pain. She thought she would try a Kinesis Contoured keyboard to see if it helped. In general, she seems to love the keyboard, but the spacebar is giving her trouble--namely, it feels a bit too high and not at the right angle, and her thumb starts to hurt after a little while. Naturally, it's a slightly different position than the spacebar on a normal flat keyboard.

Out of curiosity, I picked up the board and tried it out for a while, and lo and behold, I had the same problem--my thumb started hurting after using it for only a few minutes. In general, I love this keyboard, but if this continues there's no way either of us can use it.

So, to people who have used the Kinesis keyboard:
1) Did you have any similar problems (or any sort of discomfort like this) when you started using this keyboard?
2) Did said problems go away, or what did you do to fix them?
3) Have you ever heard of other people with the same problem? I couldn't find any similar complaints after a little bit of Google searching.

Thanks for your feedback!