Ok I am using Linux Shared hosting but found a round-about resolution to this issue.
I was getting 500 errors and their support was pretty useless, but I persisted and EVENTUALLY, they informed me that the problem was I was using FastCGI associated with my PHP files.
It comes this way BY DEFAULT.
I went into their Hosting GUI, the Extensions stuff, and changed the file association for PHP files from “FastCGI PHP 5.x” to just “PHP 5.x”
Even though there is really NOTHING in any of their sales information that says you CAN’T use this, it was on anyways.
I don’t get any 500 errors any longer and my response time seems much faster across the board.
Hope this helps.