move to AR 3.2.1, now thread behaves differently

I have this piece of code below. It used to work fine, I was using active record 2.3.8. I upgraded to active record 3.2.1 and moved some gems into a gemfile. Now what happens is rec below is an active record instance, when I enter the thread it appears to become nil. The method repopulate() is not longer defined. Why would that happen ?

... ...   def new_thread(slot,&block)     th =     @pool[slot] = th   end

... ...

  p rec.respond_to?(:repopulate) # this is fine   @tpool.new_thread(slot) do # see method definition above        Thread.current[:rset_fact] = model        puts 'in thread'        p rec.respond_to?(:repopulate) # no longer defined        rec.repopulate # error rec is nil   end