Milos Spasic

I have found the solution.

Open the wp-jquery-lightbox.php and find the following code:

function jqlb_js() {
	if(is_admin() || is_feed()){return;}
	wp_enqueue_script('jquery', '', array(), false, true);
	wp_enqueue_script('wp-jquery-lightbox', JQLB_SCRIPT_URL,  Array('jquery'), '1.3.3', true);
	wp_localize_script('wp-jquery-lightbox', 'JQLBSettings', array(
		'fitToScreen' => get_option('jqlb_resize_on_demand'),
		'resizeSpeed' => get_option('jqlb_resize_speed'),
		'displayDownloadLink' => get_option('jqlb_show_download'),
		'navbarOnTop' => get_option('jqlb_navbarOnTop'),
		'loopImages' => get_option('jqlb_loopImages'),
		'resizeCenter' => get_option('jqlb_resizeCenter'),
		'marginSize' => get_option('jqlb_margin_size'),
		'linkTarget' => get_option('jqlb_link_target'),
		//'followScroll' => get_option('jqlb_follow_scroll'),
		/* translation */
		'help' => __(get_option('jqlb_help_text'), 'jqlb'),
		'prevLinkTitle' => __('previous image', 'jqlb'),
		'nextLinkTitle' => __('next image', 'jqlb'),
		'prevLinkText' =>  __('« Previous', 'jqlb'),
		'nextLinkText' => __('Next »', 'jqlb'),
		'closeTitle' => __('close image gallery', 'jqlb'),
		'image' => __('Image ', 'jqlb'),
		'of' => __(' of ', 'jqlb'),
		'download' => __('Download', 'jqlb')
	));
}

Replace the:

'previous image'
'next image'
'« Previous'
'Next »'
'close image gallery'
'Image '
' of '
'Download'

with words on your language, save the file and upload it back to the host.

Edit image wp-jquery-lightbox/styles/images/closelabel.gif and change the text with the word on your language, save it and upload to the server.

You are done, user part of the plugin is translated now.