mountain lion upgrade installation got stuck, or not

Or that was my first and only thought for several hours. I will not fall this trap again...

I have done test driving for 10.8 with my MacBook Pro since 10.8.0 was released. Today I decided 10.8.2 is mature enough to upgrade my Mac Pro. Backups were done, recovery methods studied, file system in good condition, no problems with RAID. Downloaded upgrade, ran installer, and:

Gray screen.

Tried reboot, Gray screen. Several times.

Tried rebooting from internal recovery system, Gray screen.

Made recovery USB stick using MacBook Pro, reboot from USB stick. Gray screen.

After couple of hours searching through discussion groups and support web pages, something ring a tiny bell inside my head.

This Pro is serving several purposes: office machine for word processing, databases, spreadsheets, web pages, with attached printers, B/W laser, color inkjet, scanner, barcode reader; graphics workstation for photos, videos; music workstation with attached piano keyboard and audio interfaces; game center with attached game controllers and steering wheel as well as graphics card fast enough; entertainment center with attached TV tuner and recorder (application), DVD player, iTunes (of course), audio monitors as well as a proper sound system... AND... Video projector.

That tiny bell rang in my head and told me to switch on the video projector, and there it was: OS X installation window telling me installation is happening and will last still a good half an hour. HOW embarassing! Projector is not my primary display, so I wonder why this single window got opened on that screen. After installation everything appeared on my primary display and was perfectly fine. When system is up and running, it is easy to collect runaway windows from extra displays, during installation it is not so easy; and what is more, I have never seen this happening before. Learning all the time.

A note to myself,

Hannu