The last few hours I have been receiving 500: Internal Server Error on almost all my php pages. All other files server correctly. No change has been made to the sites in questions prior to the errors. My logs show:
Premature end of script headers: php5.cgi
Now when I researched this error I found a lot of issues that would lead me to think the scripts were the problem. But the scripts haven't changed.
I did finally find the root of the problem. I ssh into my server and noticed 10-20 processes of php5.cgi. When i deleted those processes the site began to function properly. On the site that discussed this issue they linked to a possible cause for this.
I don't know if this is the reason or not but I do know that killing the php5.cgi processes that have been stacking up on your server appears to resolve the issue for a while. I wonder if any dreamhost admins could chime in on why apache is spawning so many processes without killing off old ones and if dreamhost will be able to give us a more permanent fix.