Hi there!
 
Wanting to take IM and Stitcher for a first spin I first wanted to do upgrade with the latest patches, bringing IM from 4.0.1 to 4.0.3.
 
However, when running the installer it replies with "IM4 not found on this computer..." !!!
 
Well it´s there and launches just fine!  
 
Same thing happens with the patch for Stitcher :-(
 
I´ve tried auto install, manuallly pointing the installer to the proper folder, repaired permissions and done Unix-housecleaning with MacJanitor.  
 
No improvements...
 
I regard myself as a relatively seasoned Mac-user without being Unix-expert.
 
So folks, what´s the correct formula?

Problem fixed!
 
What happened was that I appearantly had installed the original IM/Stitcher from the user account where I do my 3D work istead of the usual administrator account. Then, when I tried to install the update from my administrator it was a No-Go...
 
Installing the update from the same account that the original SW was installled in turned out to be the clue.
 
Just to let ya´ know :-)