I had 2.9.2 before 3.0.
I had my website good to go, everything was working fine. All of a sudden out of the blue, my thumbnails were not showing up. It happens to two different themes from theme-junkie.com Bigfoot and Freshlife themes, but only when the layout is Magazine style and not Blog style.
I have tried reinstalling the theme, uploading the images once again, I also tried updating to WP3, nothing.