I solved my problem forcing a "clean" install of VS2012. ('clean' means that also the shared packages were uninstalled). Presuming that the installer I used to install VS2012 was on d:
D:vs_premium.exe /uninstall /force
Once reinstalled, the problem was gone.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…