Seriously, do NOT waste your time doing a hard reset.
WP8 is so buggy that this will either not fix it, or the live tiles will work for a short period of time and then break again.
I bought an ATT 920 at launch, and the Live Tiles worked for maybe a month. After that, updates went away. In January, my 920 burned out it's own battery, requiring me to exchange this essentially brand-new phone for a refurb. Only benefit I got was that my Live Tiles worked again. However, that did not last long, and the Portico update broke my Live Tiles again. I have done ALL of the recommended "fixes", and none of them fix it - i.e. deleting the IE cache, disabling all background apps and then enabling the Live Tiles again. And I even tried the "fix" of uninstalling the Live Tile apps and reinstalling. NONE of these things fix the issue.
I have just about had it with WP8, and am almost ready to jump back to the iOS world (which is just as buggy and flaky, but at least has a huge app infrastructure). I really like WP8, but the basic functionality like Live Tiles, which are really one of the very few advantages it has over other OS's, simply DON'T WORK....