Well there are actually some problems bringing latin back to life, and it is actually dead.
There are a lot of disagreements regarding phonemes and more, and these are things that cannot be recovered and will always be sources of dispute. As a written language these issues do not surface (as much... there are still disagreements on how to spell different words), but as a spoken language it is quite different. A non-dead language would not suffer from these issues, but a dead language needs to be reconstructed phonetically, and there is no way (short of time travel) to establish whether or not current approximations are correct.