Need to alter Marketpress list image and lightbox image size

Hi,

I just installed Marketpress and I have two questions:

1. I can't get the custom image size for the product list to work. I have the image size set to 150 wx 231h but in the list the thumbnails still display at 150x150. Is there something I'm missing on that?

2. I need to change the lightbox image on the single product page from displaying the default large image size to displaying the full size image. Can you let me know how I would do that?

Thanks for all your help.
Richard