Anyway, there is a very simple workaround. Just go to Amazon, right-click on the page and select "Edit Site Preferences..." Go to the "network" tab and under "Browser identification" select "Identify as Firefox". Reload the page and see if the feature is now working. If it is not, then select "Mask as Firefox" instead. Masking should be a last resort as it removes absolutely any trace of the browser being Opera. But, in certain cases, as with Amazon's "click to preview", masking is necessary.
Read more at http://www.cyberstream.us/post/opera-browser-website-incompatibilities-how-to-fix-them