I have had this problem through all betas of MDT 2012 and it still exists in the final release.
Conditions:
Windows 7 Professional wSP1 x64 installed using all default settings.
Installing Symantec Endpoint Protection 12 R1
Connecting to any SAMBA computer (specifically Mac OSXS.
If I install the OS using MDT 2012 (there is no issue with MDT 2010) once I install SEP the computer can no longer connect to SAMBA computers. Specifically tested with Mac OSXS but also tested with CentOS. The OS can connect with no issues before installing but once SEP touches the computer (uninstalling SEP does not fix the problem) it can no longer connect to SAMBA machines. When attempting to connect I get "The specified server cannot perform the requested operation.".
I can not find anything in the documentation or changelog for 2012 that would lead to this issue. Also this is *NOT* a problem with SEP as there are zero issues with MDT 2010.