This is an easy fix but drove me crazy for days...same thing has happened numerous times. To fix: Click on the task bar then click "show open windows." This will show the minimized version of BD "lost" in the window and there is no reason to reinstall any software.
I'd be interested in the answer to Jon's question, too. Something only available in Vista? I have the regular version of XP and you don't get that option by clicking on the task bar, whether BD is loaded or not.
After I reinstalled BD, I had the true minimalized screen for about two days and then it disappeared and since then I only have a full-screen version, even if the minimalized icon is showing. Of course this means I can't use the corrector palette at all, but you can work around that using the keyboard. It would be nice, though, to be able to see an approximate version of what the finished book would look like.