Yes, I see what you mean. I think the problem is probably related to the fact that your compiz settings are contained in a configuration folder or file in your shared /home; I'm not sure exactly where as I don't bother with compiz on my Xubuntu. Unity is very fussy about the compiz settings that are acceptable to it, and I suspect your tweaks of unity in Lubuntu will now have made unity non-functioning.
To try to get things back in unity use commands
mcduck got there whilst I was called away from my computer, but says basically the same thing. Get compiz running again in unity in Ubuntu, and then do not tweak it again in Lubuntu and you should be OK
gconftool-2 --recursive-unset /apps/compiz