thoughts--
--make a copy of file, change the end to .targz or something and try it again. try .gzip etc
--also if you found a .deb then you can find source code (targz) so you don't need this headache.
--I've cracked .deb packages before but not since the Nautilus days
--might be a tool in repo for this (I'm not sure)
--also right-click on .deb and see what else solus suggests.
edit: or just install gzip or other compression programs) in repo and see what works