asterisk users - Jan 2005 - ZT_CHANCONFIG failed on channel 11: Function not implemented (38)

I am running RedHat Fedora Core 3 with their "kernel-2.6.10-1.741_FC3"
kernel,
and if I use nethdlc in zaptel.conf, when I run ztcfg I get the message:
  ZT_CHANCONFIG failed on channel 11: Function not implemented (38)

Does anyone have ideas on how I can work around this issue?

T1 channels 1-10 are voice, 11-24 are data (second board isn't used at the 
moment).  Here is my /etc/zaptel.conf file:

span=1,1,5,esf,b8zs
span=2,0,0,esf,b8zs
fxoks=1-10
nethdlc=11-24
#clear=11-24
clear=25-48
loadzone = us
defaultzone=us