Comment 6 for bug 658719

similar issue here

did not have that package installed

figured i could install then purge it

doing so indicated

dpkg: warning: while removing canonical-census, directory '/usr/share/initramfs-tools/scripts/casper-bottom' not empty so not removed.

ls -lh /usr/share/initramfs-tools/scripts/casper-bottom
total 32K
-rwxr-xr-x 1 root root 1.5K 2010-05-17 03:53 autologin.bkp
-rw-r--r-- 1 root root 22K 2010-05-17 03:53 kdmrc
-rwxr-xr-x 1 root root 161 2010-05-17 23:58 kpersonalizer

this installation was from the kubuntu with kde3 remix, guess some of the leftovers could have been from that

casper is for the live cd (from read-only media); do not think any part of it belongs on an installed system

eventually i just removed the dir and its contents: /usr/share/initramfs-tools/scripts/casper-bottom

now
$ sudo dpkg-reconfigure linux-headers-2.6.35-23-generic
$ sudo dpkg-reconfigure linux-image-2.6.35-23-generic
both run without displaying anything about a missing casper