Are you using ATG for your terrain generation?
I picked ATG when I generated the world, I'll try a normal world and see if the problem persists just for laughs
@
Tyrindor My computer is somewhat newish I guess (2600k, GTX680, 8GB memory), FTB and everything along with it is on an SSD so I'm not so sure about it being a PC issue but who knows
Edit, loaded up a normal world and just dug, got about half durability on a diamond pick and not once did any blocks reappear, bags open instantly and GUIs open instantly...I loaded a new ATG world and did the same, it doesn't really seem to be happening on that world...I guess I'll start a new world
Edit2, Seems like a memory issue now that I look at the task manager, 2.8gig when I have 3gb allocated for FTB, chunk updates are constantly switching between 40, 100, 240, 255 while stationary in a 10 minute old world
Actually, bumped it up to 5 and 6gb, and the blocks still reappear...out of ideas