To be honest I don’t use RW to manage the resources/images. I keep them on the web host and link to them from within the project.
If you’re linking to images that are kept in a folder on your Mac, this could be causing issues.
In RW8, under Settings>Advanced, there’s a checkbox to copy site resources into the document. Have you selected that option?
If you want to find out more about warehousing, there’s a good write up here.