I installed v4 in an external runtime (long ago), never had an issue. I installed s4 no issues. I have rendered s4 with the s4 maps, and vss skin shader3 and have had no issues. I have not installed the v4 update, nor have I tried rendering without vss skin shader3. 

Instead of running the whole installer multiple times, have you all tried just running the .bat file?

note: using pro 2010 and win 7 64.