DP2M shutterbutton stuck
Can you at least get some small screwdrivers to take off the case? You may not have to take it apart much to get to the switch to blow it out a bit.
Also you could try a can of compressed air, blowing into the edges of the button. as you roll around the top in a circular motion to try and convince some of the sand to blow out. Heck, perhaps even without the compressed air if you just did that with the camera upside down it would shake out whatever is stopping it.