I have exactly the same problem!
The problem only happens when changing between Intellipad and another input method.
A couple of people are experiencing the same thing, but they're attributing the problem to Microsoft Voice Command 1.5 (which I don't have),
I have made Intellipad my default Input method, so I can type sms' if I have to, but the moment I change to another input method (Fitaly), I'm stuck with the non-intellipad methods. If I try to select Intellipad, I lose all input methods, getting the blank box, which only a soft reset will cure.