micro thumbnails don't show all images

Gallery version 2.2

Hi,

I recently uploaded new images to a gallery and altered the number of microthumbnails per column from 4 to 5. When I did so the micro thumbs continue to show the old number of images. That is there were 12 images in the gallery and after I added 3 more is still shows only 12 though it did change the columns to 5 across. Any ideas?

Thanks in advance! This is the first problem I've ever really had with gallery!!