Why do I encounter runtime error when trying to display a form with Adobe LiveCycle Designer 8.1?

While trying to display a form, I selected "Layout" in Adobe LiveCycle Designer 8.1; the following is displayed:

then the layout screen is displayed, but it's blank:

Question:  Why these are happening?  How to resolve this?

Some background info:  I had Adobe LiveCycle Designer 7.1 before, the layout screen was blank, so Live Cycle has been upgraded from 7.1 to 8.1 recently.  Any suggestions ?