This is a really irritating error, and I think, one caused by bad programming. I first ran into this error after I got a new Nokia mobile phone, and tried to install 'Nokia Network Bridge'. Aftet trying all the suggested fixes on InstallShields KB, I eventually gave up, as it wasn't worth the effort.
However, this changed when I had to re-install our Accountants workstation after a hard disk crash, and found Sage Line 50 wouldn't install, and it was pay day! After doing some googling I still hadn't found a solution, so started to dabble with the .msi files and setup.ini files. I found the setup.ini files had a line referencing the script version i.e. ScriptVer=10.1.0.238, however, we were running Version 11.0.0.28844. So I assume our script version was too new for the install program (this is what I mean about bad programming). I tried downloading and installing version 10 of the ISScript from HERE.
However this didn't work, seems you can't install an older version while running a newer one.
So, how do you uninstall ISScript? Easy, make sure you have the .msi for the ISScript version already installed, (look under "C:\Program Files\Common Files\InstallShield\Driver" for the version, then download it from the link above) then open a cmd prompt, browse to the directory holding your .msi and type MSIEXEC -X ISScript11.MSI press enter. A message will pop up asking if you are sure you want to uninstall the program, press Yes/OK, and ISScript will uninstall. Now you can either install the ISScript version you need, or even easier, just install the program you were originally trying to install, which should contain the ISScript it requires as part of the install.