I also tried launching and installing PSS studio with Administrative rights and to a different directory (not the default one under Program Files (x86) but the same thing happens.
I had the same issue on a 64bit machine but it worked fine on a 32bit machine. It was resolved on the x64 system by re-installing the gtk-sharp-2.12.10.win32.msi and dotNetFx40_Full_x86_x64.exe that are found in the C:\Program Files (x86)\SCE\Pss\software installation folder. I already had these installed so i chose to repair the installations. After I restated my machine when the FX4 repair completed, it all started to work.
I tried all of the solutions in here yesterday, and none of them worked for me. Uninstall, reinstall, repair, restart, C: drive, do it all while doing a handstand, nothing.
Magically, it works now. This is the process that I did, though it might or might not work for you (like the other solutions).
1.) Uninstall gtk# and pssuite
2.) Delete the folders where they were previously
3.) Remove the PSSuite enviornment variable (it has its own) and look in the 'Path' variable at the end for the gtk# one, and remove it as well. The last item should not have a semicolon following it. Make sure to hit 'Ok' to close that window, otherwise it won't save.
4.) Re-download and re-install as you would normally. I did mine on my K: drive, so it should work in non-default locations.
5.) Open up the enviornment variables again, and in the 'Path' variable, move the gtk# one to the very beginning. Make sure it has a semicolon seperating it from the next item, and that you remove the semicolon at the end. Again, make sure to hit 'Ok' to close the window.
6.)This might be important, might not be. On the initial startup, I navigated to the pssstudio.exe file (didn't use the shortcut on the desktop) and ran it as admin. It worked.
To modify the enviornment variables (in windows 7 at least), you can go to the start menu and in the search bar, type Environment', and you'll (hopefully) see something that says "Edit the environment variables for your account". Click on that, and you should find what I told you to look for in the bottom box named "System variables".
Moving the gtk# path to the start of the path environmental variable solved the problem for me. I had multiple applications that used some version of Gtk installed in my system.