Can't get PPTP to work

Archived from groups: comp.dcom.vpn,comp.dcom.sys.cisco (More info?)

I'm trying to get PPTP connection to work on a 3005 concentrator. I'm
following the directions in:

http://www.cisco.com/warp/public/471/altigapptp.html

In the username and password box,

if I try... the group name and password
I get... "a user attempted to log on using only group credentials"

if I try... a username and password set up internally as shown in the
above link
I get... "User not found" (internal is one of the choices listed in
authentication servers)

if I try... a username set up in Kerberos/AD
I get... "Invalid password" (and I'm positive this username and
password are working with an IPSec connection. IPSec connections
through the Cisco client are what are normally used with this
concentrator)

How can I get PPTP connections to work?

Archived from groups: comp.dcom.vpn,comp.dcom.sys.cisco (More info?)

Apparently a good reference is
http://my.execpc.com/~keithp/pptp.htm