This is often caused by a corrupted web cache file or toolbar cache.
Download FP Cleaner from
http://www.95isalive.com/fixes/fpclean.htm and
run the routines:
Clear the Hidden "Temporary" Files
Clear the Hidden Cache **.web) Files
These will be recreated as and when FrontPage needs them.
If this does not help, then also run the routine:
Restore Default Toolbars and Menus
Note that this operation deletes the toolbar cache file (Cmdui.prf) and
will remove any customisations you have made to the toolbars and/or
menus. Again, this file will be recreated (with "out of the box"
toolbars and menus) when FrontPage starts.
There is one other cause for the problem that I know of - using VML
graphics in a page that also uses relative or absolute positioning for
other HTML elements, but I cannot remember the exact details. If you
use VML (text boxes, WordArt, ShapeArt or other objects from the drawing
toolbar) see
http://www.rxs-enterprises.org/tests/VML-graphics.html
for some reasons why VML should be avoided.