Finally decided to join Creative Cloud. Downloaded the latest version of Adobe Application Manager, and I can't download Photoshop because it is listed as "Up to date." I need to fix this problem ASAP!
Note also that I previously had CS5 (master) installed on my computer (I use a Mac), but before I did any of this, I removed all apps from my hard drive (including emptying the trash). Not sure if the two are connected, but if so, I find it strange that only Photoshop is the problem when I had the full collection?
Thanks 