I purchased Lion from the Mac App Store and installed it on my mid-2009-era MacBook Pro. The installation went smoothly and the computer restarted itself on schedule. I heard the startup noise, saw the Apple logo and the spinny thing... and then it turned to this:
I let it hang like that for fifteen minutes or so before I got bored/antsy. I then forced shutdown with the power button and started it back up - same song 'n' dance. It's been doing this for thirty minutes or so now. The machine is hot and whirring away about something, but no progress is being made. It all feels very foreboding.
Do Not Enter can't be a good thing, but as far as I can Google, there are a bunch of different things it could mean. What do you think, Apple.SE?
(FTR, I have some experience with software and troubleshooting, but very little with hardware maintenance/repair/fiddling about.)
Update: As far as I can tell from Googling around and from friends' tips, this denotes an issue reading or communicating with the hard drive. I've made a Genius bar appointment for this afternoon and will report any useful information that comes out of that meeting.
Post-Genius-Visit Update: I visited the geniuses today and, long story short, I am getting a new hard drive. They were unable to mount my drive, and Disk Utility was able neither to repair it nor to reformat it. The Genius I spoke to believed that the fact that this happened to my computer immediately after installing Lion is a coincidence, or that the drive was on its last legs and that Lion was the proverbial backbreaking straw, not that the problem was caused specifically by the installation. One of the other Geniuses around also mentioned, though, that he'd seen a few cases like mine today, including the Lion part. Does this sound odd to anyone else? If not, I'll post & accept an answer saying a new HD is the solution - assuming I can install Lion on the new one without it becoming all borked up...
To be continued, I suppose.