[Plugin: NextGEN Gallery] Watermark

Hello,
I want to set watermark, but I can’t do it. I set watermark in admin panel, the picture was appeared in preview window. Then I went to gallery manager and set watermark to some gallery. WP wrote that operation was successful, but there wasn’t any watermark on picture preview.

When I tried to set up word’s watermark, it was OK and it was appeared on picture preview.

What can I do to set watermark right?