The Joomla! 1.5 installer fails to install any large module or plugin with the error message “There was an error uploading this file to the server.”
The most common reason for this problem is that the File you have uploaded is too big. The File Size Upload Limit on your Server is set too low to allow larger files to be uploaded. By default PHP allows files up to 2 MB, but this limit needs to be set to 4 MB in order to upload the Component Install File.
If you have access to the php.ini, then change or add the directive upload_max_filesize to “6M” and reload the server configuration.