asterisk users - Jul 2006 - -- Going to extension s|1 because of immediate=yes, but immediate is 'no'

We have an asterisk with a TE410P in it, when a call comes in it says :
 
  -- Going to extension s|1 because of immediate=yes
   -- Extension 's' in context 'default' from '[calling
num]' does not
exist.  Rejecting call on channel 0/27, span 2

but in zapata.conf immediate=no :

[channels]
language=it
context=default

switchtype=euroisdn
pridialplan=unknown
prilocaldialplan=unknown
signalling=pri_cpe
immediate=no

callerid=asreceived
usecallerid=yes
hidecallerid=yes
usecallingpres=yes

so I'm stuck, beacuse if in extension i put s,1,Dial(foobar/${EXTEN}) I 
really dial 's' and if I put _X.,1,Dial(foobar/${EXTEN}) I don't
even
get there because immediate=yes looks for 's'.

The strange thing is that this configuration works perfectly in other 
places, can it be that the connected nortel forces in some way 
immediate=yes ?