Showcase Theme Portfolio Problem

I am using the Showcase Theme (love it!), but I'm having a problem with the Portfolio page. The first images are in 3 columns, but the next images are in 2 columns, and not all images are shown on the page (and there isn't a 2nd Portfolio page.)

I can't figure out what I'm doing wrong.

Here's the page:

I appreciate any and all help! Thanks!