asterisk users - Aug 2004 - Cisco Router as Gateway for FXO Ports

Because of all the troubles I am having with the TDM400P cards working 
consistently for outgoing calls, I am trying to setup a Cisco router as 
my pstn gateway. The router is a 1751-V with a VIC2-4FXO card installed. 
I followed the examples at the following two links to get it setup:

http://www.voip-info.org/wiki-Asterisk+cisco+FXO
http://www.tape.net/~gerry/asterisk/cisco26x0.html

After everything is up and running, outgoing calls from my Asterisk PBX 
route just fine through the Cisco without any trouble but incoming calls 
to the Cisco are picked up and then immediately given a busy signal. Is 
anyone successfully getting this type of setup to work? Any help would 
be greatly appreciated! Thank you.

Bryan