Permissions getting set to 600

My guess is that it would be something server side that would be causing this. Honestly I would just check with your host.

I also found this previous post that sounds similar, maybe it will help:
http://wordpress.org/support/topic/something-keeps-changing-php-file-permissions-to-600?replies=2

And if you want to change the file permissions yourself here is how to do that:
http://codex.wordpress.org/Hardening_WordPress#Changing_file_permissions

Or if you want more info about permission (just thought I would throw this in here just in case) here ya go:
http://codex.wordpress.org/Changing_File_Permissions