What is Gravityv? Have you installed any other third party programs that you
could imagine would interact with MS Office (Adobe Acrobat is a common such
program, but it would not cause what you describe)?

That is certainly not normal behavior!

Can you tell if the window with the message is a Word Spell check window, or
a window from another program? What is the title in the title bar?

If no to the above, if you look in the Task Manager, can you figure out the
name of the process that is launching that window (by closing processes and
seeing which one kills the spell check dialog)?

   - Colin