We have products that are assigned to a main category as well as to a specific subcategory. (3 Levels, eg. chimneys->manufacturers-name->global-model-name)
When I choose the manufacturers-name-subcategory, all the products are displayed. Clicking on a product fires up a product page, that shows at the bottom all the global-model-name subcategories. They all have images, but there's always only the no-image.jpg for each subcategory displayed.
The main category (e.g. chimneys) has no products assigned.
I guess it's a bug.
At a first glance this sounds more like a mismatch of your image path settings and the actual location of the images. Also you can test what it looks like if you disable 'Show children category" in the Shopfront configuration. If you have access to your database tables, also check the image file titles and image file urls in the _virtuemart_medias table.
The image paths are alls set correctly. They are also shown correctly in the category view. The only place where they don't show is when I click on a product in a category which has subcategories.