I'm getting 500 errors with AJAX on the admin side. However, these errors aren't being logged in the Apache logs so they're rather hard to debug.
Is there some way I can find out what they are?
Sometimes I have a 500 error ( from NGinx ) just because I have a "character" getting outputted before the first header gets written ( or in-between ).
Activate WP_DEBUG = true and see what happens. 99% of the case I could spot the error from there. ( and it was nearly all the time the above error ).
Post back if that doesn't solve your debug difficulty problem. We'll have a look at your apache config by then.