I did set up last year Faience-Ocre as my Icon Theme and Adwaita Cupertino L Unity as my Windows Theme (the GTK+ thme was unchanged to Adwaita (default)). It has worked perfectly well until 3 days ago when starting my PC I saw the Ubuntu default showing up for Windows & Icon Theme. I noticed that at start-up the disk access LED is not lit up continuously as before but at moment stops reading for a few seconds (up to 15 s) then complete the disk reading process. When all was working well this LED would lit up continuously.

Another thing is that GNOME applications are as well not working well as previously Nautilus and Gedit now don't use the global menu in the system bar but a local window menu.

Nautilus - Nemo before the incident

Nautilus - Nemo now ...

I did open dconf to check the desktop settings in org-gnome-desktop-wm-preferences and everything is looking good. When I change the settings in the app Advanced Settings in the Theme folder I see the respective value changing in dconf. However, there is no change on my desktop.

It looks like it's crippled and GNOME related.

[Update 1]: I have the same defect as referenced @

ubuntu theme suddenly changed to default and it's not coming back!

instead of my GTK theme I get a classic, Windows-95-like grayish theme ...

However one of the solution mentionned:

http://www.webupd8.org/2011/06/fix-ubuntu-linux-mint-theme-changing-to.html

is not working at all, even for 20 s up to 60 s delay.