Has_many :through, expects "through" model to be belongs_to

Hi,
I’m using has_many and through relationship between two models
Profile and User
Profile.rb

has_and_belongs_to_many :users
belongs_to :community

User.rb

has_and_belongs_to_many :profiles
has_many :communities, :through=>profiles

When i try to do
@user.communities, Rails is searching for foreign key of user in profile
table, whereas profile and user have habtm relationship.
How to solve this problem?
Its urgent. please help