I'm experiencing some problems since I decided to upgrade Ubuntu to 12.10 version two days ago.

Firstly, I cannot select the Unity environment I previously used on 12.04 without opening the terminal with Ctrl+Alt+T and typing setsid unity.

When I select the Unity environment on the account page when I start the computer, it automatically switch back to Gnome and launch my session.

I tried to set back Unity using the setsid unity tip, and it worked fine. But after few minutes, everything freeze and I cannot control anything anymore. The only option left is to press the Power button of my Asus EeePC and switch everything off.

Question 1 : What can I do to get my Unity environment back on 12.10 from the start, without using the terminal every time? What should I do to prevent the all system to freeze once done?

Secondly, and since I cannot use Unity for new, I'm using an other interface, GNOME Shell. What's bothering me is that the Activities bar (let's call it like that, 'cause I don't know the proper name) and the Internet bar (or any bar from any other window) cannot merge into one another, reducing the display of the screen I'm actually using to peanuts!

Question 2 : Is there a way to merge those two bars? Or is there a way to hide the Activities bar when I'm not using it like on Unity environment?