Error installing linux-image-2.6.18-2-686

[Keith Edmunds <keith@midnighthax.com>]

I get an error installing the above package:

# aptitude install  linux-image-2.6.18-2-686 
Reading Package Lists... Done
Building Dependency Tree       
Reading extended state information      
Initializing package states... Done
Reading task descriptions... Done  
The following packages have been kept back:
  base-config bsdutils cpio dhcp-client exim4 exim4-base exim4-config 
  exim4-daemon-light gzip kernel-image-2.6.8-2-386 libgcc1 libgnutls11 
  libpcre3 libssl0.9.7 libtasn1-2 login mdadm mount passwd ppp tar 
  util-linux zlib1g 
0 packages upgraded, 0 newly installed, 0 to remove and 23 not upgraded.
Need to get 0B of archives. After unpacking 0B will be used.
Writing extended state information... Done
Setting up linux-image-2.6.18-2-686 (2.6.18-5~bpo.1) ...
Running depmod.
Finding valid ramdisk creators.
Using mkinitrd.yaird to build the ramdisk.
yaird error: bad value in /boot/config-2.6.18-2-686:
CONFIG_DEFCONFIG_LIST="/lib/modules/$UNAME_RELEASE/.config" (fatal)
mkinitrd.yaird failed to create initrd image. Failed to create initrd
image. dpkg: error processing linux-image-2.6.18-2-686 (--configure):
 subprocess post-installation script returned error exit status 9
Errors were encountered while processing:
 linux-image-2.6.18-2-686
E: Sub-process /usr/bin/dpkg returned an error code (1)
Ack!  Something bad happened while installing packages.  Trying to
recover: Setting up linux-image-2.6.18-2-686 (2.6.18-5~bpo.1) ...
Running depmod.
Finding valid ramdisk creators.
Using mkinitrd.yaird to build the ramdisk.
yaird error: bad value in /boot/config-2.6.18-2-686:
CONFIG_DEFCONFIG_LIST="/lib/modules/$UNAME_RELEASE/.config" (fatal)
mkinitrd.yaird failed to create initrd image. Failed to create initrd
image. dpkg: error processing linux-image-2.6.18-2-686 (--configure):
 subprocess post-installation script returned error exit status 9
Errors were encountered while processing:
 linux-image-2.6.18-2-686
Reading Package Lists... Done             
Building Dependency Tree       
Reading extended state information      
Initializing package states... Done
Reading task descriptions... Done  
#

Regards,
Keith