OS X system installation always starts on reboot.

Hello Fredrik,

Thank you for providing so much detail with the startup issue you are experiencing. I found a couple of resources that may help with the issue you are experiencing.

First, I recommend verifying Macintosh HD OS X, 10.7.5 is selected as the Startup Disk in System Preferences:

Change your startup disk for every startup

1. Choose Apple menu > System Preferences, and then click Startup Disk.
2. If necessary, click the lock icon and type the name and password for an administrator user.
3. Click the icon of the disk you want to use, and then click Restart.

You can find the full article here:

OS X Lion: Change your startup disk

http://support.apple.com/kb/PH3706

If the issue persists after verifying this setting, I recommend resetting the NVRAM/PRAM on your computer:

Resetting NVRAM / PRAM

1. Shut down your Mac.
2. Locate the following keys on the keyboard: Command (⌘), Option, P, and R. You will need to hold these keys down simultaneously in step 4.
3. Turn on the computer.
4. Press and hold the Command-Option-P-R keys before the gray screen appears.
5. Hold the keys down until the computer restarts and you hear the startup sound for the second time.
6. Release the keys.

You can find the full article here:

About NVRAM and PRAM

http://support.apple.com/kb/HT1379

Thank you for using Apple Support Communities.

Best,

Sheila M.

Hi Fredrik,

Thanks for the update. I'm glad it's working now!

All the best,

Sheila M.