Windows Picture and Fax Viewer - thinks files are Read Only?

When I browse photos saved in a folder which I access over a network, the Windows Picture and Fax Viewer will not save photos which I rotate. A message appears saying that the file could not be saved because the file is Read Only. This is not the case. If I do the same thing but on a different computer (which has the photo on its local drive) the file is rotated and saved as expected.

Does Windows Picture and Fax Viewer have a bug? If so, is there a fix/upgrade?