Error Message Trying to get property of non-object

[eluser]gazza7364[/eluser]
Hi I'm to to CI.

I have been trying the following code, to get a the drop down values in a form from a database. but I get the error
Message Trying to get property of non-object. The data is being passed to the view, has I have tested with echo print_r. The code is as follows:-

Code:

<?php echo form_open('test') ?>
*Username: <input type="text" name="artist" value="<?php echo set_value('artist',$artist->artist) ?>" />

<?php echo form_close() ?>

Any pointers will be grateful.