After all my hair became white I came across a thread: http://www.daz3d.com/forums/viewthread/8028/#105548
What I did was:
0) Deleted all my content but Genesis Essentials;
1) Open Windows Explorer;
2) Made the Program Data folder visible (it is hidden by default);
3) Entered Program Data/DAZ 3D/Content Manager
4) Tried to delete the database folder (couldn’t do it because the service was up and running);
5) Killed the DAZ Content Manager service;
6) Deleted the database folder (if there is more than one kill them both);
7) Started the DAZ Content Manager service;
8) Installed all my content again with DAZ Install Manager;
9) Humbly looked up to Heaven and asked for mercy (this is important);
10) Started DAZ Studio;
Yes… it worked…
Maybe it did because the 9th step (do it even in case of atheism).
Ahh! This fixed my problem. My Smart Content was empty after building my new computer. Even after uninstalling CMS and DS4, then re-installing, it wouldn’t work, tried doing so several times. Tried starting the CMS through start menu and it wouldn’t even launch.
So I uninstalled both again, deleted the DAZ 3D folder in program data, then re-installed DS4 and Genesis starter essentials.
Then after completing step 9 I launched DS4 and it worked! We shall see if it is still working after some time.
Edit - Still seems to be working great a few days later.