Unable to create channel of type 'DAHDI' (cause 17 - User busy)

unable to create channel of type DAHDI (cause 17 user busy)
I installed Asterisk 1.8 on Linux Gentoo 6.4 with DAHDI version 2.6.2. I installed a TDM800P card with two red fxo modules.
My chan_dahdi.conf file looks like this:
[channels]
usecallerid = no
hidecallerid = no
callwaiting = yes
threewaycalling = yes
transfer = yes
echocancel = yes
echocancelwhenbridged = yes
rxgain = 0.0
txgain = 0.0
group = 1
signalling=fxs_ks
context = from-pstn
channel = 1-8

My system.conf looks like this:
loadzone = us
defaultzone = us
fxsks = 1-8
echocanceller = mg2,1-8

When I load the card with wctdm24xxp and dahdi_cfg -vv I got following output:

DAHDI Version: 2.6.1
Echo Canceller(s): HWEC, MG2
Configuration
======================


Channel map:

Channel 01: FXS Kewlstart (Default) (Echo Canceler: mg2) (Slaves: 01)
Channel 02: FXS Kewlstart (Default) (Echo Canceler: mg2) (Slaves: 02)
Channel 03: FXS Kewlstart (Default) (Echo Canceler: mg2) (Slaves: 03)
Channel 04: FXS Kewlstart (Default) (Echo Canceler: mg2) (Slaves: 04)
Channel 05: FXS Kewlstart (Default) (Echo Canceler: mg2) (Slaves: 05)
Channel 06: FXS Kewlstart (Default) (Echo Canceler: mg2) (Slaves: 06)
Channel 07: FXS Kewlstart (Default) (Echo Canceler: mg2) (Slaves: 07)
Channel 08: FXS Kewlstart (Default) (Echo Canceler: mg2) (Slaves: 08)

8 channels to configure.

Setting echocan for channel 1 to mg2
Setting echocan for channel 2 to mg2
Setting echocan for channel 3 to mg2
Setting echocan for channel 4 to mg2
Setting echocan for channel 5 to mg2
Setting echocan for channel 6 to mg2
Setting echocan for channel 7 to mg2
Setting echocan for channel 8 to mg2

I made a simple dailplan. My extensions.conf looks like this:

[from-pstn]
exten => s,1,Answer
exten => s,n,Wait(2)
exten => s,n,Dial(SIP/1403,10,m)
exten => s,n,Wait(2)
exten => s,n,Hangup



[Incoming]

exten => 6000,1,Dial(DAHDI/1/ww1451,20,rt)
exten => 6001,1,Dial(DAHDI/2/ww1451)
exten => 6002,1,Dial(DAHDI/4/ww1451,20,rt)
exten => 6003,1,Dial(DAHDI/5,20,rt)


I attached to telephone line to my asterisk server. When I call now from SIP/1403  - I got following output on the CLI: Unable to create channel of type "DAHDI" (cause 17 User busy).

Executing [6000@internal:1] Dial("SIP/1401-00000002", "DAHDI/1/ww1451,20,rt") in new stack
[Mar 19 10:01:28] WARNING[2628]: app_dial.c:2341 dial_exec_full: Unable to create channel of type 'DAHDI' (cause 17 - User busy)
 == Everyone is busy/congested at this time (1:1/0/0)
   -- Auto fallthrough, channel 'SIP/1401-00000002' status is 'BUSY'
 == Using SIP RTP CoS mark 5
   -- Executing [6001@internal:1] Dial("SIP/1401-00000003", "DAHDI/2/ww1451") in new stack
[Mar 19 10:01:32] WARNING[2629]: app_dial.c:2341 dial_exec_full: Unable to create channel of type 'DAHDI' (cause 17 - User busy)
 == Everyone is busy/congested at this time (1:1/0/0)
   -- Auto fallthrough, channel 'SIP/1401-00000003' status is 'BUSY'

Also, Asterisk doesn’t react at all at incoming outside phone calls.
What caused this error and how can I fix this?

How can I check a line status at any channel of my TDM800P card?