The error message indicates that the user account in which you started yEd does not have the necessary rights to read the desired file from your network share. From your description, however, it seems to me that you are running yEd in the same user account you are using to access the file in Windows explorer. Off the top of my head I would think you should be able to open the file in yEd in this case. Unfortunately, since the problem lies with Java there is little we can do about it in yEd. Thus your best bet is probably copying the file from the network share to a local directory with Windows explorer, opening (and editing) the local file in yEd, saving to the local directory when done, and finally copying the modified file back to the network share with Windows explorer. I understand that this is a cumbersome workaround, but I cannot think of a more convenient solution.
