Mountain Lion Install Problems

I installed Mountian Lion on my laptop with no problems but when I came to update my Mac Mini it wouldn't boot from the disk I had made, instead coming up with a Grey Screen for ages and then just booting itself from the hard disk. When I tried to run the app the flash screen came up with "Click Continue" but when I click continue, nothing happens. I didn't want to download it again from the app store but in the end that's what I ended up doing perhaps there was something wrong with the way I had made the disk. Looking at these notes I don't remember mounting the dmg before writing it so perhaps that was it:

"If you ever created a bootable Lion-install drive, you may have performed the above procedurewithout mounting the InstallESD disk image. As of version 10.7.4 of the Lion installer, and continuing with the Mountain Lion installer, you must use the mounted Mac OS X Install ESD volume or you’ll get an error at the end of the restore procedure, and the newly created bootable drive may not function properly."

Mine is a Mac mini Early 2009 and so should be supported according to the Mountain Lion System Requirements.

Some problems others had which I found and tried unsuccessfully whilst looking for a solution:

• Mac OS X: Gray screen appears during startup: Tried this but the same result.
• Graphics incompatibility: "Some of the early 64-bit Macs sometimes have 32-bit graphics drivers... run [the following] in Terminal... if it returns "EFI32" you will have a problem":
  ioreg -l -p IODeviceTree | grep firmware-abi
  More information
  Mine returns EFI64
• Cannot install on a volume used by Time Machine for backups. Doesn't apply to me.
• Must be using an journaled drive. I am.