#8: Two people, same name. One is the Father of Noah, one is the Father of Noah('s wife, since women aren't listed). Would be a lot simpler if they said the Mothers names huh.
Maybe I'm looking in the wrong Bible, but in J's Toledoth (Gen 4:17-22) I agree with Dimattei as far as Lamech, but Gen: then says Lamech had Jabal, Jubal, and Tubalcain - no mention at ALL of Noah, so I can't see why Dimattei adds Noah to J's list.
While there's no evidence (that I've seen) for Sarevok's assertion that J'S Toledeth gives Noah's wife's lineage, there is equally nothing in Gen:4 that suggest that the lineage given is that leading to Noah. Indeed, the list given is CAIN's descendants, perhaps there as a cautionary tale?
But certainly, there's nothing in the evidence I've seen that makes clear that J's Lamech, and P's Lamech, are the exact same person. Occam surely points at "two different Lamechs" as being the obvious solution? Indeed, I can't even see where the contradiction arises!
True Story: many years back, I was listing something on ebay. A few bids had gone in (this was in the days before buyer names were hidden), and one day I received a - quite frankly - braking email from a woman who had been bidding. Seems that every time she bid, she was outbid by someone whose ebay name shared the same first name as me, and that was enough evidence to her that I had two accounts, and that I was shill bidding, and she was going to write to ebay about it. I wrote back, addressing her as "mum", and asking what she was on about, and asking if she was still coming round Sunday for dinner - and closed by pointing out that, since she had the same name as my mum, there was CLEARLY my mum, since it is impossible for two people to share the same name.
My father's name was John, and his father was William. Anyone out there want to claim to be me, because those are THEIR father's names?

Perhaps the problem is that we look at names like Methusalah and Lamech and Tubalcain, and think "no WAY would there be two people called THAT - it'd be ridiculous!". But this is, after all, an era where people thought nothing of burning their sons, or killing brothers because the cloud-spirit wasn't pleased. Calling your son Tubalcain is positively pedestrian and the epitome of suburban blandness by comparison.
Final point: In the US, in 2012, the 4th most popular boy's name was "Jayden" (WTF?)...and 5th was "Noah"(!)...86th was "Jaxon", which I've never, ever heard as a name - but clearly there are tens of thousands of them now. For girls, we see Khloe (sic), and Genesis (!!!) in the top 100.
So there happening to at some point have been two "Lamechs" in the world isn't that big a deal for me.