Category Thumbnails VM 3.0.6

[ewebzuk]

Hoping someone can help me solve this riddle.

I'm using Joomla 3.3.6 and Virtuemart 3.0.6. It's the early stages of a design for a client of mine. I've used VM many times, but this is my first use of VM on Joomla 3.

I've created the categories needed for the site, but everytime I upload an image for the category, it's not showing the thumbnail (frontend).

However, for some strange reason, 2 of the images are now showing. After changing no settings. But still, when I try to upload an image for another of the categories, the image uploads fine, and I can see it clearly in the backend, I can also see the thumbnails are being created (checking via ftp). But they still refuse to show front end.

I can supply admin login details if anyone would like to take a look at this, or if anyone feels that they might be able to help.

Thanks in advance.