some cck fields of content type not displayed (corresponding elements also not showing in devtool) Out of the blue it happened that a custom content type won't display some of the cck fields I constructed for the custom content type. This happens when I just visit the a full node of that content type. 
When I go see in firebug, I also notice that the HTML elements to those custom made fields are entirely missing. 


I checked the display options under admin->content
type->customcontenttype and everything looks the way it should. 
I checked view permissions and those are also set for anonymous and
admin roles.


Does this sound familiar to someone that cck fields cease to be displayed in full node?
You say you enabled all modules under CCK which means you probably have Content Permissions enabled.

Content Permissions module gives you per-cck-field view/edit permissions (which are all off by default!). Check that you have the correct permissions set for your fields or disable the module if you don't need that granular control.