I got this link and this one from jodawi, who in turn got them from ki. I forwarded them to my mother in an effort to protect her poor kitty India from a violent seizure-filled death. My mother wrote back to say that she hasn't used the specific Advanced Care flea control product from Hartz which these websites warn against, but that she tried using a lower strength product ("One Spot") made by the same brand and observed that it "drove India nuts" so she stopped using it and switched to a different brand that didn't make India act weird.
Since I know there are agreatmanycatlovers on my friends list (and we all know about queer women's affinity for cats . . .), I decided to pass that on.