This is something I haven't seen in 4 years. Users in SP Group "Accounting" with Contribute access getting 403b forbidden error. It was working fine until this morning. However, I log in as sp admin and go to the same library and edit the property and SOMETIMES users in accounting group are able to edit (they don't get 403 error). But they are back to 403 error.
Nothing in log. How to go by resolve this issue? (btw, users are not any other readable sp group).