I should add when I try the root "/" it says the "Can not upload image file" (or similar) and when I try an embedded directory such as "/test" it tells me it "Failed to change directory (or similar). I've tried both passive (and active) and even rebooted the cam. 
MY 5010L, stock F/W 1.00.. passive mode.
Reply Message
Test file has been sent for upload. Please check STATUS > Device Info menu to view success or failure of FTP upload. 
ftp dir:  /C/2230
FTP Server Test Failed to change directory. 
ftp dir: C/2230
FTP Server Test Failed to change directory. 
ftp dir:/
FTP Server Test Test succeeded. 
ftp dir:/C/
FTP Server Test Test succeeded. 
This camera is different.. needs / before and after. Needs folders created on server, will not auto-create like other DCS cameras (2230?)
Test images were on my FTP server.  My username was anonymous with no password, so no special characters.  _ in folder or root names might also cause issues with these cameras.