Thumbnails not showing up correctly

Hello all, since V11 we have been using the automatic thumbnail function so that we don't have to make 2 sets of images for the same product.  It worked great for a while but lately i recognized that sometimes the thumbnails don't show up correctly.  For example

http://www.ceriwholesale.com/s.nl/sc.2/category.73/.f

The first few images showed up with sort of a negative film effect but when i checked the product images they look fine.  I also checked the actual matrix items thumbnails and images and they are indeed the same.

Another example is that it i have upated a particular product and it shows up fine in the product image page but the thumbnail still shows the older version.  I double check again and the matrix thumbnail and image are correct.