Is it only me or..

Has anyone else been robbed of achievements in Halo 3?

I've beaten Tsavo Highway probably, 4 or 5 times on my new gamertag.

Once one Normal, once on Heroic and twice on Legendary.

It still hasn't given me the credit for completing Act III.

That's nuts, i've heard of having to do something twice, but 4-5 times :x Are you doing the whole thing, from start to finish?