I too have some problems with the white blank screen. It seems to happen sometimes when Montana has been suspended while you have a book open and you later open it again. The restore process doesn't seem to work. I suspect it has something to do with saving and restoring the state of the program? If you switch back and forth quickly it seems to work fine. It is when you have had Mantano suspended for a while it seems to hang.
When that happens I back out and swipe Mantano away from the list of running programs. If I start then it opens ok.