Yosemite Hangs on restart-No Help from Apple

Try booting into the Safe Mode using your normal account. Disconnect all peripherals except those needed for the test. Shut down the computer and then power it back up after waiting 10 seconds. Immediately after hearing the startup chime, hold down the shift key and continue to hold it until the gray Apple icon and a progress bar appear and again when you log in. The boot up is significantly slower than normal. This will reset some caches, forces a directory check, and disables all startup and login items, among other things. When you reboot normally, the initial reboot may be slower than normal. If the system operates normally, there may be 3rd party applications which are causing a problem. Try deleting/disabling the third party applications after a restart by using the application un-installer. For each disable/delete, you will need to restart if you don’t do them all at once.

Safe Mode - About

Safe Mode - Yosemite

Where does it hang? What do you see on the screen?

Startup Issues - Resolve

Startup Issues - Resolve (2)

we found that the issue was related to being connected to wifi - my macbook air hung while i was connected at a hotel - went to the office and plugged in a usb ethernet cable and connected to our network and it booted.

Just to be clear that we have the same issue:

On my machine, if i select 'Restart' or 'Shut Down' from the Apple menu, it quits all of the running applications, as in a normal reboot, but then it simply stops.

The Dock is still accessible, but nothing else happens (i even tried to leave it for 3 hours, with no change)

In fact, i can launch Terminal (i have it in the Dock), then, in sudo mode, type reboot and it'll finally reboot..

Note: i've compared the Console log of the machine in question with one that is not exhibiting the problem, and i think i've found the culprit:

the application 'Install in Progress' seems to start as soon as i click 'Restart', but there are no updates to install...

I'm pretty sure that this is what is happening: for some reason, 'Install in Progress' seems to think that there are updates to run, and it just hangs there, and hangs the whole system with it...

I have tried clearing the caches (using the shareware Cocktail), to no avail..

If anyone can figure it out, please help! It is driving me nuts!!

PS: there are no other error messages in the logs, and i can find no log or preference file that is associated with the application 'Install in Progress' (itself located in /System/Library/CoreServices)

I got this totally wrong...

I just figured out what the problem was:
For some reason, the internal update system in TotalFinder (an amazingly great shareware app) had stopped working, and it left an installer and some files in a folder located at:
~/Library/Application Support/TotalFinder/

All i did was trash this folder (and reinstalled TotalFinder from a downloaded .dmg for good measure), and the system is now restarting and shutting down correctly again...

i can't believe i didn't thin of that before, but for some reason, i didn't think it was related to TotalFinder..