Getting DAV access denied during Edit of Properties file

Hi,

I have to change one text in our custom Portal logon par file. So I have imported respective DC from track. Now I have to change one text in logon_nls_en.properties  file so

  1) I select this file then  click DTR->EDIT

  2) It asks for new Activity and when I click ok (after giving activity name) in Activity popup, I am getting  below error message in console. And it is not allowing me to edit

  "Edit (Failed : server response forbidden [pre|Post)] condition failed:DAV Access denied"

I have checked and I have NWDI.Adminstrators and NWDI.Developer roles .

Could you please help anybody on this. Please find the error message screen.