Error Parsing of undecoded UTF-8


I'm using RT 3.4.0 with fastcgi, MySQL 4.0.23, perl 5.8.4 on a linux Red 

Hat Enterprise 3. I had this problem on previous version of RT and i
expected to be fixed on this one but i was wrong.

My RT is working just fine, but sometimes when someone send and email to 

my RT, this person receives an email with this error:

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

pipe to |/opt/rt3/bin/rt-mailgate --queue suporte --action correspond
generated by

The following text was generated during the delivery attempt:

------ pipe to |/opt/rt3/bin/rt-mailgate --queue suporte --action correspond
generated by ------

Parsing of undecoded UTF-8 will give garbage when decoding entities at
/usr/lib/perl5/site_perl/5.8.4/LWP/ line 114, <> chunk 1.

------ This is a copy of the message, including all the headers. ------

[the complete message here]

Although the person gets this error but RT create the ticket without 

problems, and i can answer it too, but i usually receive messages from
someone asking about this message.

Any ideias. I think this problem is probably related to accented caracters.

I hope someone help me.