asterisk users - Jan 2006 - Transfer (SIP REFER) - AccountCode not available?

I have a snom 320 connected to an Asterisk server. I do some weird things
using the AccountCode as an identifier. When the snom makes a call, the
AccountCode is used successfully in the dialplan as a variable
${ACCOUNTCODE}.

When that same call is transferred using the button on the snom, I see a SIP
REFER message being received on the * server and the call is transferred -
however, this "new" call, when going through the steps of the
dialplan, has
a blank AccountCode. 

The transferred call is initiated in the correct context, meaning Asterisk
is treating it as a call from the correct user, however it seems to forget
the user's AccountCode (which is set in sip.conf).

Any ideas?

Nabeel