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