Problem with asterisk 1.6.1 & dahdi

Hi Dears
I have installed asterisk 1.6.1 and dahdi withe Digium TDM 400p
everything is ok but when i wanna Dial out from fxo i have got this error:
app_dial.c:1518 dial_exec_full: Unable to create channel of type ‘dahdi’ (cause 0 - Unknown)
i use centos 5.3

PLZ help me