I believe the cause is that current versions of AppleShare (the one built into normal MacOS) only show remote volume sizes up to 2 or 4 GB. Anything larger and it will not show the actual free space. Apple says you need to have AppleShare IP installed to see the real size. I think it's pretty much BS.. why have the consumer OS lie about the free space size on a remote volume? Anyways, there really isn't anything "wrong." You can continue to do normal file management, but you can't really tell how much free space there is on a large remote hard drive.
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Glenn
47 Ronin Multimedia
www.47ronin.com