Not sure if this has been posted already. But people that use Optimus, which is that system that switches from your Intel Graphics Chip to your Dedicated Graphics Card (e.g. GT 540M)
I actually fixed my problem of shadows / shaders not showing up even when on by going into the NVIDIA Control Panel and changing the global setting to use my 'High Performance NVIDIA Processor'. This forced Blockland to use my GT 540M chip and in turn I was able to use shadows / shaders. So yeah, try this solution if you have a Intel Graphics Chip and a Dedicated Graphics Card (Mostly applies to laptops of the sort)
Feel free to post this anywhere you like (thats if it works)