I tried going through the same process as you, but wasn’t allowed to because I’m not in America :( Did you try installing the player directly from it’s official website? If not, try installing it from here (either on Safari or Firefox) and see how that goes. If not, you may need to restart your computer for the plug-in to work (although I wouldn’t have thought so, it may be worth a try). Otherwise, you may want to have a read through this thread on Apple Discussions. The problem seems similar to yours, and although I haven’t looked through all the responses in detail, it seems as though the question was solved in the end. Good luck getting it to work, let us know how you go.