First make sure you ping the Domain (using /Applications/Utilities/Network Utility) first. Also in System Preferences->Date & Time and make sure you are using the same Time Server as the Windows Domain.
Also in System Preferences-Network highlight the connection to the same subnet as the Domain Server and at the top of the Network pane click on 'Location' Use the Location drop down + button to adda new custom named Location. Then in the bottom right of the Network pane click the 'Apply button to save that new Location. Then use the Network pane's Advance button to add the network's static route IP.
Now the steps to Join the Domain:
1. Make sure your logged in as an Administrator (System Preferences->Accounts).
2. While still in System Preferences->Accounts, highlight your Admin account (make sure the lock symbol in the right bottom of the pane is in the unlocked position) and click on the 'Network Account Server: Join' button. When pop-down comes down click on the 'Open Directory Utility'.
3. In Directory Utility highlight Active Directory and click the pencil image button. Make sure you click the discloser arrow for "Show Advanced Options" and put in all the extra info ration that is need for the Domain. Then click on the 'Bind' button.
4. Reboot and upon the reboot click the other account to log onto with you Domain credentials.
Plus check out the web site
MacWindows.com and their Reader reports about
Lion and Active Directory Tips and Reports. Those reports might help a lot in trouble shooting the Domain connection issues.
One more thing: here is a
video to watch to see it in action for 10.6.x & 10.7.x. Just make sure in 10.7 you are the latest and greatest because this .2 update fixed a lot of Active Directory quarks.