Yosemite won't install (An error occurred while preparing the installation)

[cvoro]

So, I'm trying to install Yosemite over an iMac with Mavericks.
I've downloaded it from the App Store twice (both times it was downloaded just fine) and I've ran the installer about 10 times.
EVERY time, after prompting to close all applications, when it's going to restart the system, I get this error:

"An error occurred while preparing the installation. Try running the application again"

Any clues?

 

[cvoro]

Figured it out.
I had to clear the PRAM.
After doing it the installer continued just fine and Yosemite was installed.

In case you want to try it and you don't know how to clear your PRAM, shut down your computer and turn it back on. Just before the "Turn On" sound, press the [CMD] + [Option] + [P] + [R] keys, simultaneously and keep holding them till your computer restarts again.

 

[sequel]

Figured it out.
I had to clear the PRAM.
After doing it the installer continued just fine and Yosemite was installed.

In case you want to try it and you don't know how to clear your PRAM, shut down your computer and turn it back on. Just before the "Turn On" sound, press the [CMD] + [Option] + [P] + [R] keys, simultaneously and keep holding them till your computer restarts again.

THANK YOU!!!!! I have been battling this issue for over an hour! This worked and I am now able to update the OS.