A default installation does not prevent third-party addins that may already be present on your system from interacting with Word. Some addins that might have not caused problems with Word 2003 won't necessarily play nicely with Word 2010. You should be able to see if any addins are installed by starting Word and going to File|Options|Addins. You could also try starting Word in safe mode (hold down the Ctrl key while starting), then seeing if the navigation works OK. Safe mode disables all addins, templates, etc.

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]