Devise not reading User model properly? - ruby-on-rails-3

Question

I had my app working just fine for about a year now, but I changed something I guess, and now I am getting strange Devise errors, like the below. *Note that rails console is working fine, the activerecord models (including User) are accessible as normal and I can get User.email no problem. But something is not working in the views I guess. It seems to be coming up with a no method error on User.email, which is very odd indeed. the only thing that I can think may have caused these issues is upgrading Ruby mine to latest version 6.3 recently. Maybe the gems got changed in some incompatible way?
Started GET "/" for 127.0.0.1 at 2014-05-01 18:40:12 -0700
Processing by WelcomeController#main as HTML
Completed 401 Unauthorized in 1ms
Started GET "/users/sign_in" for 127.0.0.1 at 2014-05-01 18:40:12 -0700
Processing by Devise::SessionsController#new as HTML
Rendered devise/sessions/new.html.erb within layouts/application (6.0ms)
Completed 500 Internal Server Error in 18ms
ActionView::Template::Error (undefined method `email' for #<User >):
3: <%= form_for(resource, :as => resource_name, :url => session_path(resource_name)) do |f| %>
4: <div><%= f.label :email %>
5: <br/>
6: <%= f.email_field :email %></div>
7:
8: <div><%= f.label :password %>
9: <br/>
app/views/devise/sessions/new.html.erb:6:in `block in _app_views_devise_sessions_new_html_erb__882742671_47657856'
app/views/devise/sessions/new.html.erb:3:in `_app_views_devise_sessions_new_html_erb__882742671_47657856'
Rendered C:/Ruby193/lib/ruby/gems/1.9.1/gems/actionpack-3.2.11/lib/action_dispatch/middleware/templates/rescues/_trace.erb (1.0ms)
Rendered C:/Ruby193/lib/ruby/gems/1.9.1/gems/actionpack-3.2.11/lib/action_dispatch/middleware/templates/rescues/_request_and_response.erb (1.0ms)
Rendered C:/Ruby193/lib/ruby/gems/1.9.1/gems/actionpack-3.2.11/lib/action_dispatch/middleware/templates/rescues/template_error.erb within rescues/layout (16.0ms)
Note when I added a line into the view:
<% u=User.first %>
It retrieved the first user no problem. So I'm not why Devise is confused. For some reason I suspect Warden maybe a problem, but the code in there is pretty opaque (at least for me)
Gems are as follows.
Gems included by the bundle:
* actionmailer (3.2.11)
* actionpack (3.2.11)
* activemodel (3.2.11)
* activerecord (3.2.11)
* activerecord-sqlserver-adapter (3.2.12)
* activeresource (3.2.11)
* activesupport (3.2.11)
* arel (3.0.3)
* bcrypt-ruby (3.0.1)
* best_in_place (2.1.0)
* builder (3.0.4)
* bundler (1.5.3)
* capistrano (2.15.5)
* coffee-rails (3.2.2)
* coffee-script (2.2.0)
* coffee-script-source (1.7.0)
* debugger-ruby_core_source (1.3.2)
* devise (2.1.2)
* dynamic_form (1.1.4)
* erubis (2.7.0)
* excon (0.31.0)
* execjs (2.0.2)
* fog (1.20.0)
* formatador (0.2.4)
* formtastic (2.2.1)
* highline (1.6.21)
* hike (1.2.3)
* i18n (0.6.9)
* journey (1.0.4)
* jquery-rails (3.1.0)
* jquery-ui-rails (4.1.2)
* json (1.8.1)
* mail (2.4.4)
* mime-types (1.25.1)
* mini_portile (0.5.2)
* monetize (0.1.4)
* money (6.0.1)
* multi_json (1.9.3)
* net-scp (1.1.2)
* net-sftp (2.1.2)
* net-ssh (2.7.0)
* net-ssh-gateway (1.2.0)
* nokogiri (1.6.1)
* orm_adapter (0.5.0)
* polyglot (0.3.4)
* rack (1.4.5)
* rack-cache (1.2)
* rack-ssl (1.3.4)
* rack-test (0.6.2)
* rails (3.2.11)
* rails3-jquery-autocomplete (1.0.12)
* railties (3.2.11)
* rake (10.3.1)
* rdoc (3.12.2)
* ruby-debug-base19x (0.11.30.pre15)
* ruby-debug-ide (0.4.22)
* ruby-odbc (0.99995)
* sass (3.3.2)
* sass-rails (3.2.6)
* sprockets (2.2.2)
* sql_server (0.1.1)
* thor (0.19.1)
* tilt (1.4.1)
* treetop (1.4.15)
* tzinfo (0.3.39)
* uglifier (2.5.0)
* warden (1.2.3)
* win32ole-pp (1.2.0)

Answer 1

Well, it turns out that Devise doesn't seem to like erb inside database.yml.
The change that I made that broke my app was to replace this:
development:
adapter: sqlserver
host: my_server.xxx.rds.amazonaws.com
port: 1433
database: MyDatabase
username: sa
password: the_password
with this:
development:
adapter: sqlserver
host: my_server.xxx.rds.amazonaws.com
port: 1433
database: MyDatabase
username: <%= CredentialsManager.get_db_user %>
password: <%= CredentialsManager.get_db_pass %>
While pages that don't require authentication via devise had no problem accessing the db using the new database.yml, when Devise was used, the User model it appears to be referring to has no attributes at all. (the user object represented by |f| had an #object attribute of class #, #object's attributes hash was nil. So something odd is going on inside devise when it uses database.yml to access the db. Not so sure why this is happening, but that's another thread...