The problem is that a stem will grow upwards, but then turn yellow, about 5inches up, and the leaf will not open.
Bird of paridise plant
My question wasn't answered. Why does the leaf grow-upwards a bit, and is yellow, and does not open. Please!
Can you post some pictures? That might help someone figure out what's going on. Without pictures--my first suggestion would be to start by checking your watering--could be you're watering it too much. Try sticking your finger down a few inches into the soil and see how wet it feels--if you're getting close to when you would normally water it again and it still feels really wet then your problem is probably too much water.
I agree with ecrane3. My first response was being too wet but then again without seeing the plant it is almost impossible to know. All it is, is a guess.