I have entered windhelm many times and at all times of the day, and have been playing for well over 30 hours, but this darn quest won't activate. Still have yet to see a crowd of people gathering around a body in the graveyard.

Any ideas people? I'm on PC btw

The quest failing to initiate is usually due to Arivanya getting killed. See http://uesp.net/wiki/Skyrim:Blood_on_the_Ice#Initiating_the_Quest.

Arivanya's still alive in my game

This is probably the most bugged quest in the game. Try the link Sojourner posted: there might be other things you can try there.

This quest is notorious.

The very best way to ensure that it does not bug out on you is to do it straight out of Helgen.

Trigger it by walking from Windhelm stables to the nearest farmhouse and back three times, enter the city at night.

Follow the guide on the http://www.uesp.net/wiki/Skyrim:Blood_on_the_Ice, doing things out of order might muck it up.

Since you're already a bit along in your game you could try breaking into Hjerim and seeing if you can pick up the quest from there, by investigating for clues.

It's not guaranteed to work, but it's worth a shot.

alright I'll give it a try. Time to use my master lockpicking skills lol