I have a problem adding a custom option to product. When I click on the "Add New Option" button nothing happens? And I have no clue why its happening. Any help would be highly appreciated.
If there are any try to figure out what causes the problem - you could then try to disable all custom/community modules one after the other. Disable the cache when trying that.
Also, it could help to reinstall the Core Modules through Magento Connect - you should only do that if you're really sure you haven't modified any core files (Core, template, translation, etc files) since this will overwrite the complete kernel.