For a quick fix try:
CoolResource.new(:owner => current_user.attributes)

???

or:
CoolResource.new(:owner_id => current_user.id)

Hmm, weird. Looking at your backtrace, it seems to think that current_user is an Array.
Can you try again and also do a current_user.inspect to show us what is being passed in ?

The quick fix I went for was more like:

c = CoolResource.new
c.owner = current_user

Cool. Good to know there's at least a workaround.
I have this vague feeling that ActiveRecord has similar issues with accepting real objects for associations on creation. Not sure why - it seems pretty sensible that it should accept it...
Still, I find it weird that HyRes seems to think that current_user is an Array.

could you try:
u = User.find(1)
c = CoolResource.new(:owner => u)

just to be sure it's not something weird coming out of current_user ???
It's probably not - but it'd be good to be certain.

I've had a go at it myself and I can say that using "find" it seems to work for me... but then I had to hack together a fake HyRes object. In my case my CoolResource has_one :user
is yours has_one or belongs_to?