When I get exceptions, it is often from deep within the call stack. When this happens, more often than not, the actual offending line of code is hidden from me:
I was getting these errors when trying to load my test environment (via rake test or autotest) and the IRB suggestions didn't help. I ended up wrapping my entire test/test_helper.rb in a begin/rescue block and that fixed things up.
begin
class ActiveSupport::TestCase
#awesome stuff
end
rescue => e
puts e.backtrace
end