As of late Software Updater gets frozen (won't close after checking), while
sudo apt-get update && apt-get upgradework fine. Any ideas or anybody else with the same problem?
I have Xubuntu 14.04 x64.
Update: The final answer to my question is that I have a broken system, which most probably happened when I completely removed Steam and its repository. It so happens that I've lost AbiWord, Bomi and some other apps from different PPAs and cannot reinstall them until I fix broken packages which include gcc-4.9 and four other files.
I'll wait till April for a clean install of the next stable release.