WordPress Google Cache poisoning

If you see garbage showing up in your sites google cache, you might want to have a look at your
wp-includes/general-template.php
file. Specifically the section that contains this line:
if(!(strpos($sUserAgent, 'google') === false))
It should probably not be there, and will have been deposited there without your knowledge. Remove it and wait for your site to be re-indexed.
You can test your fix before and after by using this helpful tool.