I downloaded and burned livecd-centos-7-live-gnome-201406261459.iso (checking its hashsum). It does boot flawlessly on a lenovo thinkpad T430-2349H3G using uefi only and secureboot enabled. modsign-uefi throws "Couldn't parse DBX signatures: -74", but the boot process continues. The live image, however, is not usable, neither textually nor graphically. The laptop comes with an integrated 3G modem, "Ericsson HSPA+ WWAN Minicard (H5321gw)". modem-manager.service fails to start, and subsequently also "systemd-logind.service" repetitively fails to starts, leaving the system in an unusable state, without any working tty and/or display manager. IMHO, systemd-logind tries to start getty on one of the 3g modem serial interfaces, probably not recognizing it as one, thus failing. disabling the integrated modem and wlan adapter via a physical switch is a workaround to the issue. This seems to be a fedora 19-20 bug gone unfixed into RHEL7.