How did you perform the upgrade? Following these steps worked for me in 3.0.2:
1) Extract the SDK ZIP into a new folder
2) Window > Preferences, Flex > Installed SDKs
3) Add a new SDK pointing to the extracted location
This works for existing and new projects in my workspace. Do you have any errors in your log? See <workspace location>/.metadata/.log.
Jason San Jose
Quality Engineer, Flash Builder
Thank you for the advice. After reboot the machine, the auto complete is working now.