Just a few comments for new readers or those relatively new to Linux/Ubuntu and its auto-updates functionality and impacts to stability.
Anyone who has used Windows 98 or Xp for the past 10 years for media PC/HTPC use knows that Windows Updates/Auto Updates also frequently hosed user's HTPC's- that's why in my years of Win98/XP use, I patched up the OS to be current on the day I installed the OS, then I turned off Auto Updates, then I installed and set up the media apps/codecs/etc. Zero difference with Ubuntu.
I would then only install Critical/Security patches every six months or so, making an image backup of the hard disk *before* applying the patches, as even these basic patches could often break a working HTPC.
With Ubuntu, we get a whole new distro every six months, so it makes sense to partition your drive with your /home directory with all settings and data separate from the OS/kernal partition, and simply install the new OS on top of the old one, wiping the prior OS partition. As a backup plan, you could image the older OS first, in case the newer distro has issues.
Ubuntu's Auto Updates function allows you to pick and choose the updates you want, so you could uncheck the updates related to A/V drivers, apps, codecs and media players if you want to avoid breaking something related to media playback. Also, there are really no significant security issues with Linux, except for occasional Firefox patches. If everything is working the way you want it, just disable the Auto Notify/Updates in Ubuntu, and only install a new release every 6 months or even only every year, after imaging your OS partition.
The bottom line is, with *any* OS- heck , even basic set top DVD players- if you change software (firmware in a set top DVD), you could break something. Have a backup plan, and only change something if you need a new function or to fix a known issue- if it ain't broke...