I had the same problem that keyboard seems frozen.
I think the issue is more related to "Processing". I installed "Processing" and did some coding there. I found the same keyboard frozen issue. That's why it should be "Processing", and Arduino has inherited the same bug.
I also tried to use Sun Java instead, but the problem didn't go away.
I use another trick by opening an extra "dummy" sketch, by clicking File>New. This sketch is just a blank sketch and you need not code anything in it. So you have 2 open sketches on your windows desktop.
Something like this: http://i913.photobucket.com/albums/ac331/bigtrumpet/screenshot.jpg
When you find your keyboard not responding, you can use your mouse to jump to "dummy" sketch first. And if you find your keyboard is alive again, you jump back ( using your mouse) to your working sketch
In my case, I can still leave scim running.