Single left or right mouse click will occasionally place or delete two or three blocks. This gets progressively worse over time to a point where every click will perform a double action.

What I expected to happen was...:
Single click should perform single action.

What actually happened was...:
Single click performs double or triple action

Steps to already taken to eliminate problem
1. Running Minecraft at Max FPS, render distance tiny, all graphics settings reduced to help lag
2. Checked mouse function in other games - no problem
3. Assigned max ram to Minecraft.exe