Steam Beta, can't start after update
There is a recurring problem with Steam bootloader and video card drivers. Uninstall your video drivers, and use the open source drivers to install Steam. Reinstall your video drivers after Steam is installed and working.
I think the reason is rebuilding few dependensies with Glibc 2.18 instead of Glibc 2.15 that was used before. This action newer have a pluses.
I propose one of the fixes of this problem.
1). Prepare a list of packages of Steam Runtime that based on Ubuntu 12.04 and on Ubuntu 14.04. It may look like this:
accountsservice=0.6.21-8+bsos7
acpi=1.6-1+bsos6
acpi-support-base=0.140-5+bsos6
acpid=1:2.0.16-1+deb7u1+bsos6
actkbd=0.2.8-1+steamos1+bsos1
adduser=3.113+nmu3+bsos6
alsa-base=1.0.25+3~deb7u1 A
...
xz-utils=5.1.1alpha+20120614-2+bsos7
yelp=3.4.2-1+bsos8
yelp-xsl=3.4.2-1+bsos6 A
zenity=3.4.0-2+bsos6
zenity-common=3.4.0-2+bsos6 A
zlib1g=1:1.2.7.dfsg-13+bsos3
zoo=2.10-27
2). Copy new libraries to directory with old libraries. We will got rewriting of libraries with same names, and two libraries in one directory if ABI was changed in this 2 years. For example libfreetype.so.6 will be rewritten and libopenal.so.2 will fill up libopenal.so.1. We have got one Steam Runtime for two Linux distributions (like lsb-desktop 4.1 bundle from EL5 for EL6).
3). We have been broken Steam working on Ubuntu 12.04. The reason is Glibc 2.18. All libraries that was compiled in Ubuntu 14.04 doesn't work with Ubuntu 12.04 because of 2.15 can't run binaries for 2.18, but 2.18 can run 2.0-2.18.
4). We need rebuild our package list of Ubuntu 14.04 in Ubuntu 12.04. I prefer Opensuse Build Service to make it automatically. For example this is my repository for SteamOS: http://download.opensuse.org/repositories/home:/Zenitur/Debian_7.0/amd64/
5). After rebuild all DEB's of Steam Runtime for Ubuntu 14.04 in Ubuntu 12.04 we can split two Steam Runtime's.
Sorry for bad English. I tried to make pictures with my propose.
I finished play a game and I see a window of new update. I restart Steam and I see that error window now is GTK+ 3. I don't make screenshot. I restart Steam again and it download an update. I see GTK+ 3 styled window of "Updating Steam" and "Failed to load steamui.so". Full log is there: http://paste.org.ru/?4ebo0b Sorry for my bad English.