This is both a tip and a rant. Vista RTM refused to connect to any of my SMB shares on my Mac OS X machines running Tiger (Mac OS X 10.4.8). It kept on failing with "Authentication failed" messages - even though it saw the clients on the network.

I consider myself an expert computer user in most aspects of computing - including networks. Now if I could not resolve this problem on my own and only by extensive searching on the internet found this article, I would have never solved it. How on earth will the average Joe Bloggs fix this critical issue when he goes out and buys Vista in a couple of days when it gets released to the masses?

Even though I knew Microsoft implemented SMB2 in Vista, I thought they had the savvy to ensure backwards (current?) compatibility with at least something such as Mac OS X 10.4.8. That is why I never suspected the problem has to do with an overly strict authentication policy.

Anyways... Here is the solution (taken from this site):

1. Click Start
2. Click Control Panel
3. Click System and Maintenance
4. Click Administrative Tools
5. Double-Click Local Security Policy
6. In the left pane, click the triangle next to Local Policy
7. In the left pane, click Security Options
8. In the right pane near the bottom, double-click "Network security: LAN manager authentication level"
9. Click the drop-down box, and click "Send LM & NTLM - use NTLMv2 session security if negotiated"
10. Click OK

If that does not work, as has just happened to me trying to connect Windows 7 to Mac OS X 10.7.4, try un-ticking SMB and re-ticking it in System Preferences, as explained here. Before I did that I just got this in kdc.log on the Mac:

2012-07-21T10:26:19 digest-request: kdc failed with 36150275 proto=unknown
2012-07-21T10:26:19 digest-request: guest failed with 22 proto=ntlmv1-with-v2-session