This may be a very specific problem, as I didn't have a lot of luck searching for solutions on Google. Plus, the solution may cause some (yet unknown) issues elsewhere.
Situation:
I'd try to open a network share location on a Windows Server 2003 R2 system.
Command-K, smb://ServerName/Share, hit Enter.
Error:
Connection failed
There was an error connecting to the server "ServerName". Check the server name or IP address, and then try again.
/private/var/log/kernel.log had the following in it:
kernel[0]: smb_maperr32: no direct map for 32 bit server error (0xc00000bd) kernel[0]: smb_maperror: Unmapped DOS error 1:52
Cause:
???
Fix:
I had to disable NetBIOS over TCP/IP on the Server 2003 system (TCP/IP -> WINS -> NetBIOS).
Solution (?) found here:
http://groups.google.com/group/macenterprise/msg/ddc53017b406e466
Note:
Despite what the above link says (re-enable NetBIOS over TCP/IP after you disable it), I had to leave NetBIOS over TCP/IP disabled completely for this to work. Re-enabling it just caused the same issue to occur again.