I believe the error that was discussed in this thread (http://ellislab.com/forums/viewthread/202541/) has returned in EE 2.5.2. In this version, the error reads :
Fatal error: Call to a member function result() on a non-object in /[DOCUMENT ROOT AND SYSTEM PATH]/expressionengine/third_party/safecracker_file/ft.safecracker_file.php on line 662
I tried the proposed solution of manually placing a file in the upload folder, but that didn’t fix it. I also made sure the folder permissions were correct. I did a comparison between ft.safecracker_file.php in EE 2.5.2 and EE 2.4.0 which is running on one of our other sites and I see that there used to be a check for the results before the foreach was attempted. I manually reinserted the check and that seems to take care of it.
EE 2.4.0
// Put database files into list
if ($files_from_db['results'] !== FALSE)
{
foreach ($files_from_db['results']->result() as $file)
{
$files[$file->file_name] = $file->file_name;
}
}EE 2.5.2
// Put database files into list
foreach ($files_from_db['results']->result() as $file)
{
$files[$file->file_name] = $file->file_name;
}