I ran into this exact same problem that had my PRS-300 useless for over a week until it was fixed. Prior to Sony's conversion to ePub I never had a problem authorizing and de-authorizing a computer.
The big problem with Adobe's DRM scheme is the complete lack of transparency. The fact that deactivating a specific installation does not give you that activation back is only to be learned on some internet forums.
Now apparently there's this mysterious number of activations that are added to your account over time, but what are they? How many? How often?
Sony's Bookstore and iTunes both give you ways to look up how many computers and/or devices you have authorized and what your current limit is. Both give you a mechanism to de-authorize and
give you that activation back.
Adobe must provide a self-help customer service option on their web site where a customer can see exactly how many activations have been used and how many are left. And if they won't change how deactivations work then at least provide a mechanism to request more without having to wait a week for a return e-mail or call tech support only to be told the issue has to be referred up the chain.
