I installed Flash Builder 4.5.1 and it works okay running the embedded eclipse instance, however I need to use it as a plugin in another eclipse installation, so I used the Adobe Flash Builder 4.5 Plug-in Utility.
Installation process finished with no errors (also checked the log), and I can create new Flex/AIR project and use MXML/AS/CSS editor in my eclipse installation, however no code hinting at all is available for the SDK framework classes.
I tried to:
Install it using Eclipse 3.6.2 for JEE Developers (Helios SR2)
Install it using Eclipse 3.6.1 for Java Developers (Helios SR1 - this should be the distribution used also for the embedded eclipse)
Remove Flash Builder and reinstall it
Use a clean eclipse workspace
Anyone is successfully using FB 4.5.1 with a plug-in installation?