Just a wee note to say if you are using any version ABOVE (NOT including) 1.2, then I’d have a look at this and this. The latter is probably a better explanation. Ohh and not trying to be cryptic just don’t want to alert the unwanted to this (you’ll understand what I’m wittering on about if you read those links). There is more ‘discussion’ in the WP forums if you dig for it, although it’s getting a bit messy already.
Hat tip: wee David for bringing it to my, and now your, attention.