Input method troubles

I've been at this program for only a few minutes, and I've run into a problem or two. The one that is really troublesome was with a chord identifying problem. Simple stuff, working with triads. It asks me to enter a Cb diminished chord in root position. I enter Cb3, E3 and G3. After submitting my work it gives me a '!?' symbol and tells me that I have not entered a chord. Has anyone else had trouble like this?