I updated some software using YumEx, and during the RPM transaction, the progress window went away and was replaced by a window that said something about a critical error, the "backend" and that yumex would close, which it did before I got a good chance to read the message. I can no longer start Fedora. All that happens is I see the "automatic boot in 10 seconds" page, and then the "Charge" loading screen. After the Fedora logo shows the "f" everything goes black with a small flashing horizontal bar (the text cursor) and just stays that way. No login splash screen. No mouse cursor. Just the text cursor on a black screen. I am using a LiveUSB. What can I do to fix it?