Description of problem: After a fresh F18 install from a x86_64 Live Desktop CD, when you reboot your computer, before grub2 displays your boot menu, you get an error saying: Error: PNG: Unknown Block Type. with a message saying click a key to continue. After you click, or message times out, you get grubs boot menu, in black&white, no graphics, theme failing to load. The displayed menu, albeit un-themed, works as expected. Version-Release number of selected component (if applicable): grub2 on Fedora 18. How reproducible: Always. Steps to Reproduce: 1. Install F18 using a Live Desktop DVD (Gnome) 2. Reboot after install. Actual results: Error message delaying boot, then unthemed text-only black&white grub2. Expected results: Shiny and sparkly themed grub2. Additional info: Going into /etc/defaults/grub2, changing theme from "system" to "starfield" and then running grub2-mkconfig -o /boot/grub2/grub.cfg seems to solve the problem. Therefore it seems to be related to the default theme (system) installed with grub2 rather than grub2 itself. This problem happened both with my notebook and my PC installations. I do not know if this also happens with the 4GB install DVD, or i586 versions, or KDE/etc spins, as I havent tried them.
Further investigating, I found that two files (same size/date, presumably same file in essence) in /boot/grub2/themes/system are defective/corrupt. They are fireworks.png background.png So, by 1) Switch theme back to system, 2) Replace those two files with an arbitrary PNG I created fixed the problem. I do not believe this can be caused by a corrupt download, because I always use sha256 sum to confirm download integrity, and the image did check out.
This might be a possible duplicate of bug #840179. In either case, as of now, doing a: yum reinstall fedora-logos fixes the problem. *** This bug has been marked as a duplicate of bug 840179 ***