(latest R3/Rub1.9.2) undefined method `map' for #<String:0xaea0024>

Hi,

with a simple Item.find(params[:id]) I got this little error (I
narrowed it down to that line by removing everything else until I
found the one causing the error):

Any ideas?

undefined method `map' for #<String:0xaea0024>

Rails.root: /home/mha/App
Application Trace | Framework Trace | Full Trace

rails-16a5e918a06649ffac24fd5873b875daf66212ad-master/activesupport/
lib/active_support/backtrace_cleaner.rb:72:in `block in filter'
rails-16a5e918a06649ffac24fd5873b875daf66212ad-master/activesupport/
lib/active_support/backtrace_cleaner.rb:71:in `each'
rails-16a5e918a06649ffac24fd5873b875daf66212ad-master/activesupport/
lib/active_support/backtrace_cleaner.rb:71:in `filter'
rails-16a5e918a06649ffac24fd5873b875daf66212ad-master/activesupport/
lib/active_support/backtrace_cleaner.rb:26:in `clean'
rails-16a5e918a06649ffac24fd5873b875daf66212ad-master/actionpack/lib/
action_view/template/error.rb:47:in `clean_backtrace'
rails-16a5e918a06649ffac24fd5873b875daf66212ad-master/actionpack/lib/
action_view/template/error.rb:91:in `line_number'
rails-16a5e918a06649ffac24fd5873b875daf66212ad-master/actionpack/lib/
action_view/template/error.rb:115:in `source_location'
rails-16a5e918a06649ffac24fd5873b875daf66212ad-master/actionpack/lib/
action_view/template/error.rb:109:in `compute_backtrace'
rails-16a5e918a06649ffac24fd5873b875daf66212ad-master/actionpack/lib/
action_view/template/error.rb:34:in `initialize'
rails-16a5e918a06649ffac24fd5873b875daf66212ad-master/actionpack/lib/
action_view/template.rb:53:in `new'

Actually, not true:

I found that

  @item.tags.size

was responsible - tags is an array!

If I use

  @item.tags.length

it works. Now I should clearly be able to use "size"? I use it with
other variables in the same context and only this one barks.

Latest ruby-1.9.2 (maybe that's the problem? It worked a few days
ago.)