I used to use Fedora for few years, but i wanted to change. Now I'm really novice in Ubuntu. I don't know how to describe my problem, so I try to describe last steps I've done:
Xubuntu 12.04 LTS
Acer TravelMate 2490
1) After instalation everything was fine. But I wanted to switch off bluetooth (BT) during booting the pc. I used this: rfkill block bluetooth. Then I had to forbid (ban?) bluez-applet (blueman), because after its start it switched BT on. So I use gui service settings. There I found, that the service rfkill... (+something) wasn't checked, so I did it. (Silly me! I was affraid, that this service won't start during boot).
2) Before rebooting I found in the Synaptics (Software package manager) some few *dm (xdm, sdm, etc.) packages, and I install them (I wanted to see differences...). Dependencies were OK, some few packages (ssh...?) have been added. The dialog window started, and I chose "slim" as *dm for X.
After rebooting the user bootsplash was shown (xubuntu "wallpaper" with moving stripe, which shows, that system is booting). Than black screen and nothing.
I supposed, that the problem could be with the sdm (slim) - the screen with user name and password. So I use Live cd, and changed the slim to xdm - on my harddisk (/media.../etc/display-manager). But it didn't help. So I switched it back to slim.
I attach photo of booting pc before it freezes.
I really don't know, where the problem is. Maybe between my PC and my chair.
Thank you for any help. Sorry for my language mistakes (I'm working on it).