Scribblur, there is a bug for this. I have recently learned that what is happening is that the Charmap.exe used by FrameMaker is being closed, although I don't know what is closing it. The last time I spoke with Adobe support, they said a fix is coming. Meantime, you can use the Windows Character Map utility. It's pretty much the same thing, you just have to leave FrameMaker to start it.
Barb, I've tried resetting the preferences folder, but the fix is only temporary. Strictly a one-shot.