EMET (SEHOP & ASLR) + install problems
 

I figured out the problem after about an hour of trial and error and wanted to write this for other people:

If you are installing the game, are getting an installshield error, and also use EMET to enable SEHOP and ASLR on your computer - then you should go into EMET (configure system) and disable these things. Then restart and try again. After install you can re-enable the security!

This will not apply to most people, but it was such an annoyance that I had to write up the solution =P.

Just wanted to thumbs up this one. Thanks!