This may already be fixed by Bastien's commit enabling editing of org source blocks when org-fontify-natively is not set. I can't check that now but in case it isn't here is a bug report of the behaviour I saw before Christmas.
I noticed some weird behaviour with source block editing. When source blocks are not fontified the block is greyed out as expected. Editing the block with C-c ' does NOT work except on column 0 of the begin_src line. Setting org-src-fontify-natively to t allows editing and fontifies the block natively after saving it. Following blocks are still greyed out and not editable except in column 0 of e begin_src line (using C-c ') After the block is fontified natively editing works as expected for the block. Regards, Bernt PS. Sorry if these bug reports are lacking in details... I am away for the holidays and composing these on my iPad. Emacs : GNU Emacs 23.2.1 (i486-pc-linux-gnu, GTK+ Version 2.20.0) of 2010-12-11 on raven, modified by Debian Package: Org-mode version 7.9.2 (release_7.9.2-781-g5de94e @ /home/bernt/git/org-mode/lisp/)