That is not a supported configuration. You can have a Flex 4 SWF load child
SWFs from 3.2, but you can't mix at the module level or component level.
Thanks for your response.
So, what options do I have, if I need to use a component created using the sdk 4? Should I move the entire application to flash builder?
What about installing the the sdk 4 in Flex Builder 3, but that would affect how the application looks, right?
Your only supported option is to move the whole application to Flex 4. You
can control the look via themes