References won't insert

I have a doc on Windows XP with Word 2002. I just started
having problems inserting references to some of the
headings, figures, tables, and custom items. When I select
Insert|Reference|Cross-reference all the figures, tables,
etc. are present in the list box. However, when I select
one and press the insert button the button goes down but
nothing gets inserted. They don't all fail - inserting
works on some of the cross-references but not on others.

TIA

Greg Reese