'All the time' and 'every time' have almost the same meaning as they both refer to a regular occurence, but I suppose you could argue there is a subtle difference,
The word 'every' is quite a strong word in the sense that it is specific, you might say that the difference lies in the tone. For example: A man is talking about his dog eating his shoe, he says..
A.) 'It happens every time I leave the house'
B.) 'It happens all the time.
A.) could be interpreted as having a tone of irritation to it, the man is not only specifying that the occurence is habitual, he is giving the times that the incident occurs.
B.) while indicating a reoccurence, has a feeling of vagueness to it, the man is relating the fact that his dog repeatedly eats his shoe, but it is a more neutral choice of words, so you may or may not interpret irritation in the statement.
Hopefully that's not too confusing! Good luck, Clemency