I may be a bit behind, but I seem to remember an earlier thread about the fan behavior on the MacBook. Particularly the noise and how it ceased when you were scrolling but was present when you were not. Anyway, it seems Apple has fixed the problem. Just download the new firmware update.
http://www.apple.com/downloads/macosx/apple/macbooksmcfirmwareupdate.html
http://www.apple.com/downloads/macosx/apple/macbooksmcfirmwareupdate.html