Flex works the same way with CF10.
Do you have CF9 and CF10 in the same box? Or did you remove the CF9 and installed CF10?
Remember in the Flex properties under Flex Compiler you need to have the righ path for CF10 like:
-services "C:\ColdFusion10\wwwroot\WEB-INF\flex\services-config.xml" -locale en_US
I hope this help.