ok, i found someone having a similar problem posted on .org...
http://wordpress.org/support/topic/29489?replies=23
...i was adding new categories to my blog, and the ID was incrementing just fine. i'm not sure what happened, but all of a sudden, when i went to add a new category to the 10 i already had, instead of the next one being "11", it was like 3452 or some strange value like that!
the next one would go even higher...and the next...and the next...the increment value was just exponential!
anyways, i thought i had solved it by going into phpmyadmin and selecting my wp_1_categories, choosing "operations" and manually setting the auto_increment value to 11. by the time i got back to my blog and added a new category, that value had already been reset to 3276, and i suspect if i add another category, it will change again (fixing to find out!)
so what in the WORLD has gone wrong? why is the auto_increment value going nuts like this? has anyone had this problem, and if so, have you solved it??