The launch of the SpaceX Falcon 9 this morning was aborted at literally the last second -- the sensors detected too high a pressure in a combustion chamber in one of the engines. Apparently this didn't put the rocket in any danger, but it was outside the limits for an allowable launch so the computer shut things down.
[UPDATE: SpaceX is reporting a faulty valve caused the issue, and it's being replaced. They should be ready for the Tuesday launch window.]
Here's video of the last few seconds of the countdown.
Ouch. My thoughts on this are pretty clear: it's a bummer, but then again that's all it is. Not a disaster, not a failure, just a setback. These are complicated, complex machines, and delays are inevitable.
The good news is there's a backup launch date of Tuesday, May 22, at 07:44 UTC (03:44 Eastern US time), and another the next day, May 23, at 07:22 UTC. Hopefully, this glitch can be fixed and the rocket launched on one of those dates.