Whenever you are missing images, left click the red X you see, and click properties. it will show you exactly where you need to place the image.
With photopost, I typically copy the style directory into the gallery directory. ie:
http://www.tech555.com/gallery/redbar/
If you do this, it will correct your image problem. The image in question should be here:
http://www.tech555.com/gallery/redba.../menu_open.gif
Also, realize this is COPY, not move the images.. yes, you will have two copies of the redbar folder on your server. This is what I do, but someone else more familiar with photopost might know the better way to do it.