I can’t say this will fix it for everyone, or will even be the cause of your 500 error. Earlier today an epic battle played out between Windows Live Writer and the WordPress install this site sits on. More specifically, I was greeted with a “500 Server Error”.
In my server logs I found the following:
[25-Apr-2011 17:43:30] PHP Fatal error: Allowed memory size of 33554432 bytes exhausted (tried to allocate 122880 bytes) in /wp-includes/class-wp-xmlrpc-server.php on line 2769
Out of memory? What? After some searching I came across this article by Asif Rahman which listed 4 possible solutions, of which #1 fixed it for me:
Add the following line to the wp-config.php file:
With luck and judging by the number of posts asking for help when I Google’d around this should help some others out.