I can think of one example here in B.C that I find quite frustrating.
A friend of mine who is a missionary to the native people has had a lot of success in reaching the native people with the gospel. However one thing that he finds rather frustrating (and I have experienced this as well). Is even when some native people seem to be Christians for a few years and see fruit in their lives.
You can be with them and they would see a raven or another animal and they would say something like: "I think that is my uncle".
They are not joking either, because in some native cultures they believe that when someone dies they are reincarnated into an animal.
In many cases it doesn't seem to matter how much they read the Bible, they don't seem to realize that Christianity doesn't mix with their former religions.

Tom