Failure to copy on Blue Ring 500GB MyBookWorld

I am having problems copying files to my MyBookWorld 500GB (blue light) NAS. Transfer of large folders fail from both my Windows XP machine and my MacBook, though the exact symptoms differ by platform.

When the transfer fails, I am unable to add any additional files or delete folders until I reboot the drive.  All is OK after reboot and I can add and delete more files and folders as long as they are not “too big.”

Windows Symptoms -------------------
On each try, I get approximately 730 MB of a 25 GB folder copied.  Then, I get the following message:

Error Copying File or Folder  [X]

Cannot copy filename: Access is denied.

Make sure the disk is not full or write-protected

and that the file is not currently in use.    [OK]        

Macintosh Symptoms  ------------------
Approximately 130MB of a 15GB file transfers before an error message appears:

ooo   Copy

The operation cannot be completed because you

do not have sufficient priviles for some items.            

[Stop]  [Continue]         

If you click continue, you get another message:

ooo   Copy

You may need to enter the names and password for an

administrator on this computer to change the itemfilename.

 [Stop]  [Continue]                 

Clicking on continue yields a similar message.

I get the same pattern whether I log onto the drive as the administrator or as a regular user.
One platform oddity… on the Windows side I can go into the drive and delete individual files without reboot.  I cannot add files or folders and I cannot delete folders.  On the Mac side, I can add/delete nothing (file or folder).

Model Number:  WDG1NC5000N

Firmware: 02.00.15

Mionet has never been installed.

Any help?