Incidentally, I chatted with Dez and managed to solve this problem.
Go into the page customer/main/products.tpl and change the product_thumbnail include to something like this:
Code:
{include file="product_thumbnail.tpl" productid=$products[product].productid image_x=150 image_y=150 product=$products[product].product}
where
x is width
y is length
As ATKO girl mentioned settings the y value isn't recommended unless all thumnails are exactly the same dimension. In this case remove image_y=150
Hope this helps...