I work for a company that uses PCs and we have an FTP site to upload graphic files. Myself and others who are using MACs can not upload to the FTP using Safari. The company FTP disc shows up on the desktop but when I drag the file into the window I get a message that says the disc can not be modified. Another empty window opens too and if I drag the file in there I can see the actual image not the icon of the file. What am I doing wrong?