It's important to note that when using the move_uploaded_file() command, that some configurations (Especially IIS) will fail if you prefix the destination path with a leading "/". Try the following:
<?php move_uploaded_file($tmpFileName,'uploads/'.$fileName); ?>
Setting up permissions is also a must. Make sure all accounts have write access to your upload directory, and read access if you wish to view these files later. You might have to chmod() the directory or file afterwards as well if you're still getting access errors.