Hi Neil,
Do note that the 'Find' panel sometimes misbehaves in a document with endnotes (ie you select an endnote entry and nothing happens). This mainly seems to affect documents with content after the endnotes, when that content is visible.
Have you tried repairing your Word installation? With Word 2010, you do this via 'Progrms & Features' in the Windows Control Panel. Beyond that, try the approaches suggested here:
http://support.microsoft.com/kb/921541
http://word.mvps.org/FAQs/AppErrors/...artingWord.htm and
http://windowssecrets.com/forums/sho...hp/32641/page2
for various troubleshooting steps that will help you track down (and hopefully solve) the problem.