I'm a newbie to all this - couldn't stand using NeoOffice etc any more so have taken the plunge and started learning LaTeX a few weeks ago - I love it! Obviously LOTS to learn but this forum is a great resource and I look forward to using it.
I managed to fix this problem by checking my .bib file for missing year entries (very easily done using BibDesk and probably most similar software - just sorted all entries by year and edited/removed those with the years missing.) Re-ran everything and didn't have any problems.