Hi,
For the last month I have had 500 internal server errors on my brand new wordpress site and other errors listed in wp supercache. I use godaddy on a shared windows server. It was very intermittant and very annoying. I have been scouring the web for solutions and tried many to no avail. However, I wanted to post to this website because I found something that worked instantly for me. It is a plugin that installs through the wp plugin screen. It is called “nginx Compatibility (PHP4)” and I found it by searching the plugins with the term “fastCGI” since that seemed to be my problem. I don’t have nginx but this plug in said it fixes 2 problems one of which seemed to be mine because it mentioned mod_rewrite. I was a bit hesitant because when I clicked on the plugin’s website, it is written in another language and I could not find the ENGLISH link. But since I was at my wits end and felt like I had nothing to lose, I tried it. To my surprise, my pages now load within a few seconds and I can reach the admin page! Marvelous. I hope this helps someone.
good luck