I decided to roll-up both of these questions into 1 post, but mods, please feel free to let me know if you don't like this. With that said.... So, I'm am currently about to initiate 3 website/app ...

I've got 2 VPSes running Wordpress. Both are running the same version of Wordpress and MySQL (newest for both). The two sites are running vastly different themes. One works fine. The other VPS though.