indows Server 2008 and Net RPC SHUTDOWN problems

[ToddAndMargo]

Hi All,
Host: CentOS 5.5 x64
Guest: Windows XP Pro SP3
Guest: Windows Server 2003 x32 SP2 R2
Guest: Windows Server 2008 x32 SP2 (not R2) <-- the one with problems
VM: VBox 3.1.8

On a customer's server, I have three Windows guests: XP, Windows Server 2003 Sp2 R2, and Windows Server 2008 x32 SP2 (not R2). Problem: the first two respond to Samba's "net rpc shutdown" command. The 2008 server ignores it.

I have the following on the 2008 server: 1) File Sharing enabled, 2) "Use Sharing Wizard" (simple file sharing?) off, 3) RPC Locator server on automatic and started, 4) Remote Service Management (RPC) enabled in the firewall.

I am stumped.

Many thanks,
-T