I setup Server 2008 R2 running Active Directory and now Win7 clients who are members of the domain can no longer see/access our OS X File Server. Doesn't show up in Network, nor can it be accessed by \osxservername. Did I break something, or is there a way to get around this?
Sounds like a name resolution problem to me at first blush. Can you PING the OS X server machine by name and IP address from the computers where users are having the issue?
Could also be that domain policy has modified the NTLM vs NTLMv2 settings in the clients, too, preventing authentication from working. Anybody know if the OS X SMB server supports NTLMv2 yet?
PING works by name? How about accessing the server via a UNC with the IP address? If that works then you've definitely got a name resolution problem.
In the DNS forward lookup zone for your AD domain add an "A" record for the OS X server's name and IP address and I predict things will get a lot better for you.