There is a bug to do with setting the Mac model (then posting it in the database). You can make the below modifications, or use the file attached. 

Edit the file -

Windows - c:\xampplite\open-audit\code_igniter\application\models\m_device.php

Linux - /usr/local/open-audit/code_igniter/application/models/m_device.php

Change line 1107 from:

$data[] = $value;

to

 $data[] = (string)$value;

You should also change line 1335 from:

$data[] = $field->value;

to

$data[] = (string)$field->value;

I have attached the revised file if you simply want to replace it.

Apologies for any inconvienence.

Mark.

m_device.php