AutoCAD & CADWorx Plant keeps saving as read only

I use AutoCAD 2014 with CADWorx Plant 2014 on Windows 7, 64-bit operating system saving onto network drive.
I keep running into problems with complex drawings saving as "read only". I've double checked all the settings I can find to make sure it wasn't something I was inadvertently doing but cannot find a way to prevent it. It doesn't seem to happen on simple 2D line drawings, just complex 3D CADWorx drawings. It will do it while I have the drawing open - I will have opened the drawing, made changes, saved progress periodically, then all of a sudden I can no longer save progress because it's read only?
Has anybody else run into this issue? Any suggestions on how to keep it from happening?