When I just loaded my singleplayer world, Many of the things I have built have sections missing.
In fact, One of my Houses are missing! An Entire House!!!
Along with that, some blocks have been replaced.
I would never do this, even some of my larger buildings have entire walls missing.
Heres My list of missing or replaced....things
Missing:
An Entire house
The Entire back section of my City Hall
Three different walls, steps, and the wood floors of my Tavern, and my bathroom, for some reason....
The Wood floors and steps of my School House
Some Items I placed in a couple chests
Some wood blocks are missing
My City Pool is full of dirt, only one Block deep of water, it was cobble sides, and smooth stone on the bottom, and even had some steps to get out, and my diving board is missing a block
Some dirt pathways that I dug out are filled in... again
And my mine was filled in.
Replaced:
Some wood blocks that I used in my floors were replaced with dirt...bloody dirt (and yes, that was a reference to the Yogscast)
And some cobble was replaced with, you guessed it, dirt.
I will post some pics ASAP
The Version I use is 0.4 dev 20120606
I have Windows