Quote Originally Posted by Arkhios View Post
Who told you that? Because there's no basis for such a claim. Nowhere in the books does it say a paladin that takes a level in another class would lose any paladin features.

Sounds like the someone who did is an ass.
This was the case in 3.X and prior, paladins that took levels in other classes could never go back. So either house rule by nostalgic DM or a carry over because DM is mixing editions.