I'm helping Erandur relieve the people of Dawnstar from the nightmares on the quest 'Waking Nightmare'. We're in the tower, and I'm at the part where I need to drink the Vaermina Torpor.

Twice already it has frozen when it autosaves when I open up my menu (items, magic, map, and skills). So I turned that off. But I tried to save it manually right before Erandur performs the ritual spell. It froze.

What should I do? I'm on Xbox 360, have all updates possible, the Hearthfire DLC, and the game was downloaded from the Xbox Marketplace. It would seem as if this downloaded game is more glitchy than my original Skyrim disc.

Should I delete all autosaves, disable them, and then try to complete the quest without saving it?

I think you would get more help in the Skyrim issues fourms.So sorry can't help.

Turn auto-save off.

This quest has a glitch where anytime you save after drinking the Topar your game will always freeze. Save right before you drink the topar and then you have to finish the quest without saving.

Once the quest is complete and you exit out Nightcaller temple you may resume saving as before.

http://www.uesp.net/wiki/Skyrim:Waking_Nightmare#Bugs

It's the first bug listed. They go a bit more into detail in the discussion page. Just follow what I wrote in this post and you'll be fine.