Dira,
Did you also include this line in the index.html file?
<script type="text/javascript" src="widgets/Streetview/streetview.js"></script>
That little line has all the Javascript functions for allowing Flex to speak with the Streetview API.
Also,
In the index.html file search for the word "theApp" in my file. This will also need to be in your file for the communication between the flash functions and the javascript functions. If you havn't done any customization to your html file I suggest overwriting it with what I supplied. Let me know if this helps, I'm always available to help.