AutoCAD LT :: Read-only File Opening From Sharepoint Library

we have problem opening read only files with Autocad 2012, 2013 from Sharepoint library. When user opening dwg file directly from Sharepoint library (with Share point webdav, from Explorer for example) to which he have only read only access,  Autocad gives error

„Drawing file is not valid“. The same result for UNC path (\intranetprojekceRizeniProjektu64ArchivProjektu102575) or mapped drive.

When he use Autocad open dialog to find the file in Share point library and use „Open Read Only“ from dropdown, file is opened fine.

Also if user have write  access rights to library (when I add him rights for writing for this library), autocad works fine.

We need opening files directly in Sharepoint library (not to download them to users computer) cause DWG files have attached another DWG files from library as XREFs.

May be the problem could  be caused by DWL files, which cannot be created in read only library, whilst autocad didn’t recognized the library is read only. But we didn’t find how to disable DWL files in autovcad 2012 or higher.