I shudder to think that Cisco has such a potentially huge security problem in their VPN clients.
I just fired up vpnc and it seems to work, and I'm not seeing the DNS issues.
The trickiest part is matching the terminology in the vpnc README to the Cisco profile file. The "IPSec" ID and secret in vpnc are the group name and password in the Cisco profile. The Xauth username and password are the user name and password in the profile.
The group password can be recovered from its "encrypted" form in the profile using the form linked from the vpnc web page.