It will not be up to Google to prove to you how they caught what they deemed as fraudulent clicks on your site. They will not show you the IPs of those who clicked. Instead, explain to them in a very professional manner that you never caused invalid clicks and send them your logfiles to help prove your case.

You have to remember that the first responsibility of Google is to satisfy their advertisers, where the money comes from; and not the publishers. They need to protect the interests of advertisers at all cost. As a result, any clicks perceived to be less than above-board are investigated oftentimes leading to the cancellation of the account of the advertiser.

There have been many cases of publishers whose account was initially disabled but reinstated from the program. Here are some threads from Webmasterworld.com of such cases:

http://www.webmasterworld.com/forum89/5960.htm
http://www.webmasterworld.com/forum89/9886.htm

I suggest you contact them, email them in a professional way explaining your side. It can be helpful if you send in your logs. Then wait if they respond.

If they don't respond or don't accept you back, explore other contextual advertising options such as

Yahoo! Publishing Network (currently in beta and available to US publishers only) http://publisher.yahoo.com/
Intellixt http://vibrantmedia.com/site/web_01a5.htm
Quigo Adsonar http://www.quigo.com/adsonarexchange.htm
IndustryBrains http://www.industrybrains.com
Commission Junction Evolution http://www.cj.com
Kanoodle Brightads http://www.kanoodle.com/about/brightads.html
Clicksor http://www.clicksor.com/affiliate_programs.php
Contextweb http://www.contextweb.com/
Bidclix http://www.bidclix.com/
References :