I've heard that there were problems with some of the Upgrade SNs distributed. If you contact Customer Support, they should be able to straighten it out quickly:
Let us know how it goes,
Well, all I can say is that I have EXACTLY the same issue as the OP and after one hour on the phone with Adobe support (including "elevation to the highest level") I have gotten exactly nowhere. I even sent them a link to this thread. All support personnel can tell me is that I might have to pay for a "support incident" to resolve the issue. Mind you, this to install a product (upgrade) I've paid them for! If they DO refuse to do anything unless I purchase a support incident then you can be sure they're getting the upgrade back (in the form of a block on the payment with my CC company).
I like the product but if this is an example of the skillset of Adobe support it will be impossible to use it in production.
That's alarming. I'm sorry that Support didn't help you on this.
I've escalated this to our Product Manager, and expect he'll contact you soon to help iron out the problem.
Well, I hope so. Companies make mistakes, it's how they handle them that's important. I especially enjoyed the support rep's comment that this was "an issue that is completely new" to Adobe.
Thanks for taking the time to try and help me out.
I am sorry that our support team were unable to resolve this for you.
Can I ask you to contact me off-list with your Flash Builder 4.0 serial number so that I can investigate further and get this resolved for you as quickly as possible?
My email is shorten at adobe.com
Group Product Manager, Adobe