Comment 7 for bug 1183204

Something like this affected me as well. After my first startup after installing unity-tweak-tool my Unity icons had reverted to the default icon set. The gtk theme was unchanged.

I can't remember if I opened unity-tweak-tool before I restarted. I then tried to reset the icon theme but the Unity icons did not change (the gtk theme did). After uninstalling unity-tweak-tool I still could not change the icon theme (using ubuntu-tweak). After a restart changing the icon theme worked as expected.