I just upgraded my home PC to Windows 7 Ultimate 32 bit. After trying various methods to get the Cisco VPN client to work, I gave up and decided to just run it in XP mode. The last steps I tried were in this article ( http://social.technet.microsoft.com/Forums/en-US/w7itproappcompat/thread/d880dfe5-7f44-4955-8620-2a9355d8ea8b/ )
After that, I uninstalled the Cisco client and rebooted. I uninstalled the Deterministic Network Enhancer and rebooted again. Both uninstalled successfully, but now I'm not able to resolve any DNS.
The only way I can resolve DNS is to reinstall the DNE, reboot, and uninstall the DNE. Then I am able to resolve DNS lookups until I reboot again. Once it's rebooted, no more DNS.
Edit: I completely forgot I'd asked this question until harrymc posted his answer. I've since found out that to fix this problem, I need to disable my Local Area Connection and re-enable it. Once I do that I have no trouble making network connections until the next time I reboot at which point I repeat the process. It's annoying, but manageable since I reboot very infrequently.