If you're unable to see a widget you've enbeded, You'll want to make sure you've got the most recent version of flash by navigating to http://get.adobe.com/flashplayer/ as well as javascript enabled within your browser. If after you update your flash and you still don't see the widget you'll want to clear your cache.

For Internet Explorer 8, follow these steps:

1. From the Safety menu in the upper right, click Delete Browsing History... . 
2. Deselect Preserve Favorites website data, and select Temporary Internet files, Cookies, and History. 
3. Click Delete.

For Internet Explorer 7, follow these steps:

1. From the Tools menu in the upper right, select Internet Options. 
2. Under "Browsing history", click Delete... .
3. To delete your cache, click Delete files... .
4. To delete your cookies, click Delete cookies... .
5. Click Close, and then click OK to exit.

Firefox 3.5 and above for Windows

1. From the Tools menu, select Clear Recent History... .
2. From the Time range to clear: drop-down menu, select the desired range; to clear your entire cache, select Everything. 
3. Click the down arrow next to "Details" to choose what history elements to clear (e.g., check Cookies to clear cookies). Click Clear Now.
4. Back to top

Steps for other browsers can be found here.