System error Concerning Samba

[Stephen]

When I connect my laptop to my samba network on my Ubuntu 12.04 box, and 
then shut down the lap top I get a system error on my desk top that is 
running Ubuntu.

A pop up box asks me if I am running a windows server. I tell it yes and 
it did work properly on Ubuntu 10.04.

Both computers can connect with each other, and I can transfer files 
back and forth from either one. There doesn't seem to be anything wrong. 
After I shut down the lap top is when I get the error.

Is there some way that I have to log the lap top out of the samba 
network before I turn of the lap top?

I have used Google and other searches to try and find out but have found 
nothing.