Steps to reproduce.
1. In the OptimizeGoogle options, go to the Images section and check the "Rewrite links to point straight to images" checkbox.
2. Perform a Google Images search.
3. Click on any of the returned images, the image alone will load in your browser as the links from the results screen have been correctly rewritten.
4. Perform another Google Images search.
5. This time, before clicking on any of the returned images, click the "Show options..." link at the top left. You don't need to change any of the options, simply displaying them is enough to trigger the bug.
6. Now proceed to click on any of the returned images. This time you'll get the default site behaviour with the Google frame at the top of the page and the whole page that the image comes from at the bottom i.e. the links are no longer rewritten to point directly at the image. This behaviour will continue even if you click the Back button and hide the options again; the only way to 'reset' things to get the rewritten image links again is to perform another image search.
The impact of the issue is that you can't have your images links rewritten if you want to use any of the options on the image search page (e.g. if you wanted to only look for Large sized images).
Using Firefox v3.6.2 and OptimizeGoogle v0.77.
Thanks for the detailed report!