Kernel panics after installing Cisco VPN client for Mac
This kernel extension if it is on your mac will probably cause a kernel panic in 10.6.
com.cisco.nke.ipsec 2.0.1
As I documented on this page earlier only AnyConnect is compatible with 10.6. The older Mac Cisco software should not be used or it will panic. Cisco has no plans to update that software. You can read someone who did some troubleshooting and traced the problem to the installation of the Cisco VPN client here. In addition this page has more resources about troubleshooting Cisco VPN with 10.6 or Snow Leopard.
Not true. I use the regular Cisco client all the time and am running 10.6.3. You do need to have the latest version of the client though. The version I am running is 4.9.01.0180. You should uninstall the old version prior to installing the new to ensure that nothing is left behind that could cause a problem.