An anonymous reader writes with an excerpt from Tech Fragments that says "NASA has yet again postponed the launch of Space Shuttle Discovery, which was due to launch today, because of a hydrogen leak in the vent line between the external fuel tank and main engines. The vent line is at the intertank region of the external tank and is the overboard vent to the pad and the flare stack where the vented hydrogen is burned off. ... The NASA launch team is resetting to preserve the option of attempting a Thursday night liftoff at 8:54 p.m. EDT depending on what repairs are needed and what managers decide. The Mission Management Team is meeting at 5 p.m. today to discuss the issue."
You can watch for updates on NASA's Space Shuttle page