I have tested this on two different computers with the same browser and it seems that lightbox plugin to resize bbcode images linked from external sources or via URL is not working.
I have set a max-width and max-height via css for bbcodeImage so its automatically resizes to a smaller size and so you would get a resize option.I can't confirm this. The 2 situations you mention don't use lightboxes - we only use the lightbox for attachment thumbnails, which you can see here: http://xenforo.com/community/threads/test2-embedded-image.59569/
I am using the default style with modifications in CSS and may be some jquery plugins of my own, the error occured only when I upgraded my browser and still works well in lower version of chrome and all versions of firefox. Well thanks for letting me know where the bug might be in and I will look into my modificationsYou've got custom behaviors/styles/CSS there that may well be interfering. What you have shown a demo of isn't something that is lightboxable.
You need to take this back to a default style and build up to see where the problem potentially appears, though keep in mind that style modifications aren't something that we can support.