The title pretty much sums it all. I've had had to uninstall the software temporarily on my computer, but forgot to proceed to deactivation before proceeding.
Now I've reinstalled it, but I'm stuck at an activation screen which prompts me to either buy a new licence or quit. I've checked my account, and my licence is still active and valid.
Is there any way I can get AA3 back on its feet?
Your problem goes deeper than forgetting to deactivate--Adobe have actually closed the activation servers for Audition 3 and a number of other bits of earlier software. However, in a strange way this will work to your advantage now!
Visit this page http://helpx.adobe.com/x-productkb/policy-pricing/creative-suite-2-act ivation-end-life.html for instructions on how to download and install a generic version of AA3.0 with a standard serial number. This should get you going.
I gather a few people with Audition 3 pre installed have encountered some problems installing the new download (but not many). If you're unlucky enough to be in this group, the FAQ tells you how to fix the issues: http://forums.adobe.com/message/5117676#5117676