Quote Originally Posted by Alex80 View Post
"difference between неправду говорили and неправды говорили"

It's just grammatical case.
Hmm... I'm not so sure about that. I mean the latter is more like telling lies over and over again Although, the former can and probably should be viewed as telling lies in that manner, not just once. All in all, the one with plural неправды makes it more defined and colorful in my opinion.