grouped_collection_select for has_many :through Association not Updating

I have a scenario where I created a few has_many :through associations which I am having trouble updating. I do appreciate any help! Thank you!

Here is my setup:

    ruby 1.9.3p392     Rails 3.2.13

Here is the scenario:

    I have 3 models that are related     There are many Industries, many Keywords, and many Conferences     Industries have many Keywords     Conferences have an Industry     Conferences choose Keywords based on its Industry

Keywords has a basic CRUD model. Creating an Industry then adding Keywords works fine.

My relationship for Conferences, Industries, and Keywords is where I am having issues. I am trying to update Conference information, change the Industry that it is currently associated with, choose new Keywords based on the new Industry all in the same form. When I remove the Keywords element out of the mix, the update works. But when all three are there, then I get the errors.

The view renders fine but when I submit a change, I get an error. The error that I am seeing is:

**Couldn't find Industry with ID=3 for Conference with ID=1**

My relationship for Industries and Keywords are: