David
The script is working here in CS6 There are one or two traps to watch out for. If neither of these work for you, then I'll need more information.
1. Don't have the 64 bit version of PS open when you run the script. You may recall that quite some time ago (Imatch 3.6 days) you asked me if it was possible to have the script trigger the 64 bit version of the program, rather than 32 bit. After a lot of searching the answer seemed to be no. A 32 bit application like IMatch can't access the 64 bit registry, which it would need to do to trigger and interact with PS 64 bit (although note #2 below for a recent exception to this). So if you have PS closed when you run the script, it starts the 32 bit version. If the 32 bit version is open, it just uses it. However if you already have the 64 bit version open, then IMatch tries to use it but it can't. I'm fairly sure that's your problem.
2. As per the post of peterjohannes above, if you have CS installed and then also install one of the recent CC versions of PS, you'll have the problem he described. In recent versions, only a 64 bit version of PS is installed, and given this, something gets jumbled between 32 and 64 bit when IMatch calls PS. The solution is to uninstall both CS6 and CC and reinstall only one. As reported by peterjohannes, the script works just fine on the 64 bit only version of PS CC. I've still got CS6 on the desktop, and CC on the laptop, and the script runs fine on both.
[So the question is, why is IMatch not able to trigger the 64 bit version of CS6, but is able to trigger the 64 bit version of CC? I can only guess that for PS CC, since there's no 32 bit version, Adobe must put some magic stuff in the 32 bit registry that points to the 64 bit version. They can't do this for CS6 as the 32 bit registry has to point to the 32 bit version.]