Upload error - The file could not be written to disk

[eluser]PermanaJ[/eluser]
Im trying to upload image, but I get this error message

"The file could not be written to disk"

Dont want to get confuse with file permission, i set the folder 777. What could be the reason that error happen ? I use this setting :

Code:

...

$upload_cfg['upload_path'] ='./images/photos/';
$upload_cfg['allowed_types'] = 'gif|jpg|png';
$upload_cfg['max_size']    = '200';
$upload_cfg['max_width']  = '200';
$upload_cfg['max_height']  = '200';
$upload_cfg['encrypt_name'] = true;

...