This is not a proper solution, just a work around so that setting dialogues work (I have the same issue). This only seems to happen with the default elementary GTK+ theme. If you switch to another theme (HighContrast is also installed by default) then the issue is gone for me. Alternatively using the default theme, but then switching to dark also works for me (that's what I use now). Forcing a re-install of elementary-theme (sudo apt-get install --reinstall elementary-theme) does not solve the issue.
This is not a proper solution, just a work around so that setting dialogues work (I have the same issue). This only seems to happen with the default elementary GTK+ theme. If you switch to another theme (HighContrast is also installed by default) then the issue is gone for me. Alternatively using the default theme, but then switching to dark also works for me (that's what I use now). Forcing a re-install of elementary-theme (sudo apt-get install --reinstall elementary-theme) does not solve the issue.
See also http:// elementaryos. stackexchange. com/questions/ 2744/ui- elements- are-not- displayed