включите дебагер в фотосете и посмотрите ошибки
в файле \engine\lib\internal\template\js\main.js найти строки

custom_settings : {
			},

			// Debug Settings
			debug: false
		};
		
		ls.hook.run('ls_swfupload_init_options_after',arguments,this.swfOptions);

и debug: false изменить на debug: true, сбросить кеши (и лучше отключить компрессию файлов)
внизу страницы добавления фотосета появится дебагер

SWF DEBUG:                         SSID=a9f0d3dbb4517ca97ccf55b216dcfcf8
SWF DEBUG: ----- END SWF DEBUG OUTPUT ----
SWF DEBUG: 
SWF DEBUG: Event: fileDialogStart : Browsing files. Multi Select. Allowed file types: *.jpg;*.jpe;*.jpeg;*.png;*.gif;*.JPG;*.JPE;*.JPEG;*.PNG;*.GIF
SWF DEBUG: Select Handler: Received the files selected from the dialog. Processing the file list...
SWF DEBUG: Event: fileQueued : File ID: SWFUpload_0_0
SWF DEBUG: Event: fileDialogComplete : Finished processing selected files. Files selected: 1. Files Queued: 1
SWF DEBUG: StartUpload: First file in queue
SWF DEBUG: Event: uploadStart : File ID: SWFUpload_0_0
SWF DEBUG: Global Post Item: security_ls_key=9c4471c05877a3bc3a947666f4d11a6b
SWF DEBUG: Global Post Item: ls_photoset_target_tmp=6bf1f9d76c
SWF DEBUG: Global Post Item: topic_id=
SWF DEBUG: Global Post Item: SSID=a9f0d3dbb4517ca97ccf55b216dcfcf8
SWF DEBUG: ReturnUploadStart(): File accepted by startUpload event and readied for upload.  Starting upload to http://site.ru/photoset/upload for File ID: SWFUpload_0_0
SWF DEBUG: Event: uploadProgress (OPEN): File ID: SWFUpload_0_0
SWF DEBUG: Event: uploadProgress: File ID: SWFUpload_0_0. Bytes: 32768. Total: 66282
SWF DEBUG: Event: uploadProgress: File ID: SWFUpload_0_0. Bytes: 65536. Total: 66282
SWF DEBUG: Event: uploadProgress: File ID: SWFUpload_0_0. Bytes: 66282. Total: 66282
SWF DEBUG: Event: uploadError: HTTP ERROR : File ID: SWFUpload_0_0. HTTP Status: 401.
SWF DEBUG: Event: uploadComplete : Upload cycle complete.

а оно все равно крутится… и нету варнинга что типо фотка залилась