I saw you had problems with a different plugin SEO Friendly Images as well. Can you give me a site URL where you are experiencing this problem? I’d like to resolve the issue for you if possible.
Sorry, but i delete your plugin after the image trouble. The “DP ALTerminator – Missing ALT manager” works fine with alt tags AND images 😉
It sounds like you probably had a plugin conflict, maybe you had a similar plugin active? Most likely that caused the JavaScript errors that caused those images to fail to load. Sorry my plugin couldn’t help you.