Both "Keep your distance" and "Unlife is strange" won't unlock for me.
I've fetched all 11 ranged weapons (got a 12th one, which is the preorder gun) and the plant in Ried's room grew, which Jonathan commented accordingly.
For me these 2 are the only achievements left and it bugs me, that they don't unlock.
It's also 4 days ago that I met the requirements, so it's very unlikely that it's sort of a XBOX live problem.
Please look into this and patch it. There seem to be other people who have problems with several achievements not unlocking too