X-Files ? strange ! script behaves differently when running as cron task....

I am running a ruby script ( 1.9.2, w Rails3 gems)
this script reads 2 different pop3 mailboxes then send back emails to
senders with a specific link in the email body...
for testing I send one email in each mailboxes
joinus@domain.com and unase@domain.es

running the script in the server console is fine .... the 2 mailboxes
are read, and each sender receives back the corresponding responses

then I created a cron task to run THIS same script every 5 min

/5 * * * * bash -c "source /usr/local/rvm/scripts/rvm && rvm
gemset use rails3 && /usr/bin/env ruby /var/www/../current/jmy_app/
joinus_email.rb"

the script is launched correctly, my info log shows the notifier being
processed for each email as above , BUT only the first email response
is delivered....

as the script runs well in the console, I don't know where to start
looking for some weird coding ...
I have the following setup :

my_app_folder
- joinus_email folder
    - joinus_email.rb
    - notifier folder
        -notifiers..html.erb

I defined the ActionMailer::Base.smtp_settings in the script
joinus_email.rb... from which I am building the emails and delivering
them

joinus_email.rb
require 'action_mailer'
require 'mail'
...
def send_email_back_to_sender(..)
   mail = Notifier.joinus_email(..)
   mail.deliver
end

any clue welcome ..

First clue .. running in the console ... no error .. but
when running the script as a cron task, I receive a message from the
cron daemon :

/usr/local/rvm/gems/ruby-1.9.2-p136@rails3/gems/actionpack-3.0.5/lib/
action_view/template/handlers/erb.rb:129:in `valid_encoding': Your
template was not saved as valid US-ASCII. Please either specify US-
ASCII as the encoding for your template in your text editor, or mark
the template with its encoding by inserting the following as the first
line of the template: (ActionView::Template::Error)

# encoding: <name of correct encoding>.

now what should I do with it ? any complementary clue ?