Have a look at this thread at Adobe Forums - http://forums.adobe.com/thread/606832
The above thread is about the exact error message.
In all there are following things suggested in the thread.
1.
Associate the Flash Debug player as the standalone player with SWF
files.
2.
To use HTML wrapper, just right click on your project and select
'properties'. Select 'Actionscript Compiler' on the left column, and
in the resulting properties pane on the right, check the option for
'Generate HTML Wrapper File'. That should force FB to launch the web
browser for debug. This will require the ActiveX or Mozilla flash
debug player, depending on which browser you're using for debugging.
3.
I did a search in the registry and found two instances where Flex was referrenced rather that Flash builder changing this to flash builder seemed to eliminate the problem.