Hey,
maybe you are not running the Nginx documentation (Unofficial (Community) ) configuration required for ownCloud?
If you are using this configuration then i just have found a small problem in it. Instead of:
oc[sm]-provider/.+||core/templates/40[34])
it should be (without the doubled ||
):
oc[sm]-provider/.+|core/templates/40[34])
I have asked the ownCloud team to update it in Updates for the nginx community configuration