The experience required to levelling up has been increased a bit. So, when you required 10000 before, you'd now require 12500 or so - that's why percentage went down. You didn't lose any, but you need more to level up.
Reason for this was that it was really low, and people were skipping quests / levelling from 32-33 in less than an hour.
So - very well noticed, and I'm surprised you did, but that is on purpose. Group up, kill some monsters, and you'll be back at the EXP you had in no time. If a map does not have enough monsters for you to level up quickly, let me know what map and monsters you're levelling on, and I will make sure that the map is "busy" enough that you can level at a good pace.
