Fatal Error Cannot use string offset as an array

I am using a form with file upload with code as follow.
I get the error message:
Fatal error: Cannot use string offset as an array in drupal614\includes\form.inc on line 984 when form is submitted.
Any solution for this error?
Thank You

print drupal_get_form('contactform', $form);

function contactform($form){
$form['name'] = array(
'#type' => 'textfield',
'#title' => t('your name'),
'#default_value' => $object['name'],
'#size' => 30,
'#maxlength' => 128,
'#required' => TRUE,
);

$form['eMail'] = array(
'#type' => 'textfield',
'#title' => t('your email-adress'),
'#default_value' => $object['eMail'],
'#size' => 30,
'#maxlength' => 128,
'#required' => TRUE,
);

$form['subject'] = array(
'#type' => 'textfield',
'#title' => t('subject'),
'#default_value' => $object['subject'],
'#size' => 30,
'#maxlength' => 128,
'#required' => TRUE,
);

$form['message'] = array(
'#type' => 'textarea',
'#title' => t('your message'),
'#default_value' => $object['message'],
'#size' => 30,
'#maxlength' => 128,
'#rows' => 7,
'#required' => TRUE,
);

$form['file1'] = array(
'#type' => 'file',
'#title' => t('attach your files here '),
);
$form['file2'] = array(
'#type' => 'file',
);
$form['file3'] = array(
'#type' => 'file',
);

$form['submit'] = array(
'#type' => 'submit',
'#value' => t('send email'),
);

$form['#attributes'] = array(
'enctype' => 'multipart/form-data',
'id' => 'contactform',
);

return $form;

}

// validation function for the contact form
function contactform_validate($form_id, $form_values) {
// first we validate if there is a email injection
$finds = array("/bcc:/i",
"/Content-Type:/i",
"/Mime-Type:/i",
"/MIME-Version:/i",
"/multipart\/mixed/i",
"/boundary=/i",
"/subject:/i",
"/cc:/i",
"/to:/i");
foreach($form_values as $value)
foreach($finds as $find)
if(preg_match($find,$value))
form_set_error('', '

Stop spamming

');

// then we validate the email-adress
if (!valid_email_address($form_values['eMail']) && !empty($form_values['eMail']))
form_set_error('', t('Please check the spelling of your email-adress.'));
}

// submit function for the contact form
function contactform_submit($form_id, $form_values) {

$headers = array();
$mailkey = 'contact-with-attachment';
$from = $form_values['name'].' <'.$form_values['eMail'].'>';

$recipient = 'web_administrator@xxx.com';

$subject = $form_values['subject'];
$body = wordwrap($form_values['message']);
$reply = 'Thank you for your interest.';
$goto = '';

if (!flood_is_allowed('contact', variable_get('contact_hourly_threshold', 3))) {
$output = t("You cannot send more than %number messages per hour. Please try again later.", array('%number' => variable_get('contact_hourly_threshold', 3)));
drupal_set_message('

'.$output.'

');
drupal_goto($goto);
}else{
if(file_check_upload('file1')){
$trenner = md5(uniqid(time()));
$headers = array('Content-Type' => "multipart/mixed; boundary=$trenner");
$message = "\n--$trenner\n";
$message .= "Content-Type: text/plain; charset=UTF-8; format=flowed;"."\n\n"; // sets the mime type
$message .= $body."\n";
$message .= "\n\n";
for($i=1;$i<=3;$i++){
$file = file_check_upload('file'.$i);
if($file->filename){
$file->filepath = str_replace("\\","\\\\",$file->filepath);
$message .= "--$trenner"."\n";
$message .= "Content-Type:$file->filemime;\n\tname=$file->filename\n";
$message .= "Content-Transfer-Encoding: base64\n";
$message .= "Content-Disposition: attachment;\n\tfilename=$file->filename\n\n";
$filedata = fread(fopen($file->filepath, "rb"), $file->filesize);
$message .= chunk_split(base64_encode($filedata));
$message .= "\n\n";
}
}
$message .= "--$trenner--";
}else{
$message = $body;
}

// send mail
drupal_mail($mailkey, $recipient, $subject, $message, $from, $headers);

// Reply
drupal_mail($mailkey, $from, $subject, wordwrap($reply), $recipient);
//drupal_mail($mailkey, $from, $subject, '<>', $recipient);
// Log the operation:
flood_register_event('contact');
watchdog('mail', t('%name-from use contact form', array('%name-from' => theme('placeholder', $form_values['name'] ." <$from>"),)));

drupal_set_message('Your message has been sent to us.');
drupal_goto($goto);
}
}