Also getting this error on 1.6.2 with CPT’s.
Tried disabling all plugins, inc metabox and reactivating, and flushing/changing/resaving permalinks.
Again, if i mark as draft I can edit the post/page etc but as soon as its published i get the error. Frontend 404’s when post/page is published also but fine in draft frontend preview
@itchycode what nginx settings should we be looking out for or checking?
EDIT - Also on 1.6.1, 1.6 & 1.5.7 - so either serious bug or site errors somewhere.
EDIT 2 - worked out that my errors could be due to trying to edit a CPT child - new bug report here - MetaBox CPT hierarchical children Invalid Post Type