As an experiment, try installing the photoshop cs5 12.0.4 update from here:
Does it work?
It's also possible you need to update to a later version of the Adobe Application Manager:
I went to Adobe's registration page to reenter my serial number. This webpage is here:
When you use that link and are signed into Adobe.com with your Adobe User ID and Password you should see a page the has the Products you have registered. If you have ever activated CS5 you will see it listed as one of your registered products. If you then click on the listed CS5 you Product key will be displayed. Use that key when you install CS5. If you have an available activation CS5 should install and be activated. If you have used you two activations you need to deactivate one of the first. If you can not deactivate one because of a disk crash or some other machine failure you need Adobe assistance to activate your new machine install. When I use that link the page I get displayed look like this:
Also this link may help with your update problems. Use the CC Cleaner Tool to solve installation problems | CC, CS3-CS6
I tried the "experiment" you recommended. I downloaded the 55MB update file, then installed the update from the explicit download. The update installed. Now when I bring up Photoshop (in my copy of CS5-Extended), and click on "Help --> Updates" - that update (Photoshop 12.0.4) no longer appears - the other 4 updates, however, still appear.
So I guess this means there is nothing in my copy of CS5-Extended (on my computer) that is preventing the installation - it is something else. This may be an important clue.
I appreciate the info. I did as you suggested and to my surprise, my copy was registered on 8/11/14. I installed it and (I thought I activated on Windows 7) in March (approximately) this year. So the 8/11 date must be the result of me trying to fix my status with Adobe, and something happened though I did not know it.
Over the last few days I have read that I was supposed to deactivate my copy of CS5-Extended (bring up Photoshop, then go to Help --> deactivate) before uninstalling Photoshop on Windows XP that I was going to replace with Windows 7. I did a clean install of Windows 7 (not an upgrade install), so had to reinstall CS5-Extended. It may be that my issues are a result of not deactivating it before changing my operating system.
enough chatter ... I will go see if things are now working.
If I need to contact Adobe Assistance ... do you by chance have a phone number? I have called Adobe Customer Care (800) 833-6687, selected the Photoshop option, and was told this option is not eligible for talking with someone, directed me to the forums or chat rooms. (Chat room people - I have chatted three times - none of them had any clue whatsoever on what might be wrong or how to fix it).
You can search for the updates you need here:
Or you might try installing this later version of the adobe application manager
Adobe support is not what it should be. But if your problem turn out to be that your two activation are in use and you can not deactivate one because of a machine failure makes that impossible. Only Adobe can help you. Their customer support is able to help for I have had to have them help me with that problem twice in the 20 years I been using Photoshop. You need to get an Adobe support person to do their job and not pass the buck.
I been using Photoshop since version 3 around 1994-95 time frame I skipped version 4 and 6. Versions 3 and 5 are no longer listed in my products. So it look like I've only used Adobe product since 2001.