Merriam-Webster online has it spelled both ways, but "payed" only applies to one out of seven definitions, as in "the entire rope has been payed out." All other definitions would be "paid."
Slow as it may get at times, this is why I looooove Firefox: M-W Online is among the search engines available in the address bar (along with Google, Bing, Yahoo search, Wikipedia and even IMDB), without having to bookmark the site. All you need to do is type in the word or phrase in the dialog and hit "enter."
+1 on DTV's attitude re spell checkers. I don't know how many times I've caught the one in MS Word offering misspellings for correctly spelled words. >rant Mister Softee may be omnipresent, but that doesn't mean he knows everything! >/rant