Hi JR,
Please see Mehul's detailed post on using Bing maps in the ArcGIS Viewer for Flex in this thread:
How to access Bing Maps
Hope this helps,
<map initialextent="-13123600 4025400 -13105800 4033950" > top="40">
Hi JR,
Noticed this typo in your <map> tag, you need to remove the extra ">".
Hope this helps,
Are you using Viewer 2.1 or an earlier version?