Winmobile 6.1, HTC Diamond2, 800x480 screen (if that matters):
Sequence:
1. In Spacetime, open the device default on-screen keyboard (pressing icon in low-right corner)
2. Switch to "Today" screen, or any other application that will use entire screen
3. Switch back to Spacetime.
Result:
Lower portion of screen except the bottom status bar (i.e., where the default keyboard should be) is not rewritten by either Spacetime or the default keyboard. Also, screen presses in that area go to the application "below" (e.g., Today).
Subsequently, first press on the keyboard icon in the low-right corner opens the default keyboard, second press closes it and redraws Spacetime bottom area. Hinting that after switch to Spacetime some portion of it thinks the default keyboard is in "off" state. While some other portion of it does not re-activate lower portion of Spacetime own screen.