When browsing the "Network" one server doesn't show up

We have a small business with two Windows 2003 Servers.  A domain controller/file server, and an Exchange 2003 server.  We have about 30 client machines running XP Pro and Win 7 Pro.  The other day I noticed that when I go to view my network devices in "Network" (used to be "my network places" in the old days), I don't see my exchange server listed.  I also have a Linux Mint computer I was playing around with, and it also doesn't show my exchange server listed under the "Samba Shares".  I see my DC server, and all the workstations listed, but the Exchange server isn't listed.  I can successfully "ping" my Exchange server...I can successfully browse the couple of shared folders on the Exchange server...our email works fine...but it doesn't show up in the "My network places"/"Network".  What can I look at on my exchange server to see why it doesn't broadcast itself over my network places?

This brings up another issue I've had with this server too...and it might be related.  We have a login script on our domain controller that is automatically run when users log in.  This login script just maps network drives from our domain controller server primarily, but there are two drives that get mapped from the exchange server too.  Often when viewing all the mapped drives on a workstation, the two drives that are mapped to the exchange server have red "x"s on them...yet when you open up the mapped drives, they connect instantly and no longer show the red x...at least for a while...and they they get "disconnected" again after some time period.  Simply clicking on them magically reconnects them, but it's just another odd behavior.