Hey everyone, I replied to a thread on the "troubleshooting" board but thought I'd do this one too as it might have more traffic.
I just got my reader yesterday and am having this problem. Installed all new ADE and Sony eBook Library. Problem still happens. My husband borrowed a PDF book, I borrowed a ePUB book. Only one can be read while the other is protected. This goes both ways, depending on how it was put on there (I re-checked out, put them back on a bunch of times).
My husband wanted a Kindle and I wanted the Sony - this is going to make him want to return it for the Kindle!
Has there been any solution to this problem?