Two computers must be running in order to access LS-WVL/E

[scribe5]

On my LinkStation LS-WVL/E. I have it set to auto on a network with 5 computers, some wired some wireless. All run Windows 7 32-bit Home Premium. The Linkstation wakes up when any one of the computers is turned on. However, I can only  access NAS files from any of the computers when another computer is turned on--I.E. at least two computers need to be on for any or all computers  to access the NAS. If only one is on, and I try to access, I get a message that a user name and password is needed. I don't have a user name or password and it was not set up that way. But that message doesn't pop up if two or more computers are on. A Buffalo tech suggested I leave the NAS on all the time...and that worked. But one of the reasons I bought this NAS was because it has an auto detect/on function. Any suggestions are very welcomed.