I'm out of ideas then, sorry. The product buttons don't use Flash, so it has to be an Opera issue.

All I can suggest is that you uninstall Opera completely and do a fresh install of the latest version in case something from one of the older versions is still hanging around and interfering with operation.

Revo Uninstaller is a good way of ensuring a total uninstall - the Windows uninstall process sometimes leaves stuff behind. The free version will do the job for you.

Before you uninstall, read this article on migrating your settings to make sure you don't lose your bookmarks etc. Note that it's a little out of date - the opera6.adr file is now named bookmarks.adr, but as far as I know it's ok to rename your old opera6.adr bookmarks file.