can't get lower case "h" to type

We have an imac that refuses to type a lower case h. It will type an upper case one just fine. It displays them fine as well. I checked the fonts on it to make sure none were corrupted and I also got rid of all the keyboard shortcuts in casce they were messing it up. Also tried changing the keyboard. This is a mac that's used in a classroom so it's hard telling what the kids could have done to it. Any ideas?

Does it type shift + h (H) and option + h (˙) and option + shift + h (Ó) ok?

And also have a look at the h key on the keyboards the kids are using. Pull off the little plastic key and have a look underneath. Something like a little dust might be affecting it.

And lastly have you tried using the h anywhere, and when it fails to type check what console has to say?

And there used to be an app called key caps on OS 9. I can't exactly remember the name but it was just a keyboard. And the key pressed would light up on the keyboard on the screen. Came with the system I think. If there is an OS X alternative to this, it would be useful to test if the mac itself can see the h key being pressed.

Thanks for your suggestions, I am able to do shift + H to get a capital and so on. When I opened console in the background and tried to type it didn't say anything. When I open the Keyboad Viewer and hit "h" nothing happens and I get a message on the console saying "Unknown Class NonAcceptKeyPopupButton In Interface Builder" Is this related to my problem or does this always happen? I'm totally at a loss with this. Any help is appreciated