Because OS 10.8.2 was the worst update in Apple history, for the first time ever I decided to do the 10.8.3 update on an external boot disk before sacrificing my internal disk. I used Super Duper to make a bootable clone of my internal , booted from the external and then did the combo update. It seemed to be ok although they didn't fix the scroll bars in Safari as I had hoped. The first app I tried was Photoshop CS 5.1. It tried to open but I got a window that said "could not inialize scratch disk because disk could not be found". After I clicked OK on that, another window said "could not open because disk could not be found" . I have never tried to open Photoshop any version from a bootable backup before and I don't know what this means. The scratch disk for Photoshop is set to be my internal drive Macintosh HD. Why would it not find it? If I were booting from my internal and had set the scratch to the external it would find it. Why would the app be looking for itself on another disk?
After recloning my internal which is still 10.8.2, I have not yet booted from the external to see if the problem was somehow caused by 10.8.3, but I wouldn't be surprised if it was. People have reported the usual weird behavior of an upgrade already on forums, but not this paricular problem
I am runninga 2011 mini with dual i7 and 8 GB of RAM.
Reset your preferences...as Chris said, the directory path of your drive where your prefs were is not available so you need to reset the prefs...or not and not be able to run Photoshop, your choice.
If you have 2 volumes with the same name, they really have different names under the hood.
Photoshop is telling you that it cannot find the scratch volume that you specified - which means that the volume you specified is no longer available for some reason.
But this means you can not open Photoshop from a backup disk. I think you're telling me that I somehow have to set the scratch and the native disk in preferences of the Photoshop app on the internal boot disk before making the bootable back up so that the back up can find them. That is not possible. I have never heard of such a thing. All my other apps open from the booted back up.
This sitaution means that Photoshop will only open from the original disk installtion. "Zis cannot be!" as Professor Strelzoff used to say after filling a blackboard full of equations.
No, you still are not getting it...the PS preferences on the backup drive you created using SuperDuper was set to use a specific drive as the scratch disk...that drive is no longer available (as Chris has told you). So, you need to reset the PS preferences which will then default to whatever drive is the current boot drive. That will allow Photoshop to open normally where you can then go in and change the scratch preferences to whatever current mounted drive you want.
You are making this much harder than need be. Just reset your preferences, ok?
The key combos are checked early in the startup process, so try it!
Keep in mind there's a key combo just for resetting the scratch disk choice. It's two keys I believe, but I couldn't tell you which ones without doing a search - you can do that search as well as I can now that you know the possibility exists.
Can't reset the PS preferences on the booted external because Photoshop will not open, un;ess you're telling me that the key press sequence while opening it will still work.
While holdong down Command/Option/Shift, double click on the Photoshop app icon...you'll get a box asking if you want to reset the prefs, say yes. Then Photoshop will start with default prefs.
I've had Photoshop since early 1996 and I have never reset the preferences because I never needed to. I'll take everyone's word for it that this will work. Actually I've never worked on anything where the location of the scratch disk made any difference so I always leave it on the boot disk. I find it strange that the clone does not do what it should do, just open. This means that the app is identified with a particular physical disk through the preferences, which is generally not the case with other apps.
I've had Photoshop since early 1996 and I have never reset the preferences because I never needed to.
Since the first day of release of PS 2.5 for the PC, I have used the program almost daily on some major projects and extremely large Images. I have only had to trash my Prefs once, and that was when I had a major system crash, during a Save_As operation. Some users, seem to have to do that on a quarterly basis. Not any help regarding your situation, but just another PS-user, who has almost never trashed Prefs, and that has been over almost 20 years.
Good luck with your particular issue,
Just to be clear, resetting the Photoshop prefs is troubleshooting 101. I'll admit that since Photoshop CS and OS X, the need for resetting the prefs has gone way down (although I had a lot of problems when Photoshop first included GPU).
However, if you EVER have a hang/force quit or an actual crash, you should seriously consider resetting the prefs because, well, in a hang or crash, that's when pref can get corrupted...afterwhich Photoshop can misbehave and cause problems.
But in this case, resetting the prefs was a fix for the issue where the exact directory path for a scratch disk no longer existed and thus kept PS from even launching...
Although the OP hasn't given an update, I'm 99.9999% sure his Photoshop is back to launching correctly...and that the issue was fixed by trashing the prefs.