On paper, the answer is that you can use robots.txt to diallow Googlebot while allowing the Adsense bot.
http://www.google.com/support/webmas...366&topic=8846
However,
There's recently been a change where all the various google bots feed a common cache, to reduce the need for multiple spiderings of the same page. So it really depends on your goal for keeping out the bots. If all you want to do is stop caching, there's a meta tag for that.
see also
http://www.mattcutts.com/blog/crawl-caching-proxy/
http://www.mattcutts.com/blog/bot-ob...ing-googlebot/