You should see the latest kernel version is probably not 18.104.22.168. Maybe it is. If isn't there, you can't expect bash to understand invalid syntax.
At the empty prompt,
then hit tab, enter another letter, wash, rinse, repeat until you get the version you want.
dpkg -i --force-all linux-image-2.6
if you must use 30.5, try trac.offensive-security.com/repository/browser/backtrack/macroverse/l/linux/linux-image-22.214.171.124_126.96.36.199-10.00.Custom_i386.deb?rev=1