Put the summary of the bug you're having here

What I expected to happen was...:
I wanted to place some blocks for a roof on my home on Sky-sg.com Creative Server.

What actually happened was...:
I placed a block, and it deleted it and the one before it. Also, server lag stops everything and erases some of the blocks i have just placed.

Steps to Reproduce:
1. Rapidly place blocks of any kind
2. Server lag comes...
3. BAM! The block is just an eraser.