Field Permission Issue even without Field Permission Module I ran into a strange issue. 

I have a content type with a field for user-reference (say XYZ). Now, I used the module nodeaccess_userreference to grant the referenced users in the field XYZ the permission to edit the node. 

The edit button did show up and the referenced user was able to edit the content except for one field : "Body" field!! 

I've no module for field permissions or anything like that. Why is it happening? All the fields are editable. I've been trying to debug the issue but so far no clue. 

Kindly suggest what the problem might be or some approach to debug it.

I will update here as soon as I find some solution. 

UPDATE:
The issue has been resolved. It was a text-format permissions issue. If anyone ever comes across such an issue, be sure to check your text-format permissions. They are the ones that never cross your mind.
Sorry to trouble you guys, but I figured it out just now. It was really a silly mistake from my side, but I had been hitting my head ever since. 

Anyways, turned out that I had not provided the permission to the user for that particular text format!! The article was created by admin using "Full HTML" but the user had no permission for that format.

Anyways, I figured it out using a hack method which was really cool. 

The text box was showing this message when it denied permission : 

This field has been disabled because you do not have sufficient permissions to edit it.


I copied this and searched for this complete sentence in the contributed as well as core modules' directory. The "culprit" was filter.module. The function which was doing this was properly commented and said that "deny the users with no permission to the given text format".