Extra “0” at the bottom of Archive list

There is an extra “0” at the bottom of my Archive list that links to the latest month. I have read in this forum that this probably has something to do with a post with a “bad” date, and have tried to find it in phpMyAdmin looking at the wp_posts table, but am not finding anything wrong.

I am looking in all four columns in phpMyAdmin with dates:
post_date Descending
post_date_gmt
post_modified
post_modified_gmt

As far as I can see everything is in the correct format, e.g. 2009-07-xx xx:xx:xx

Is this what I should be looking for? Should I be looking anywhere else?

Thanks very much.