Blocks in a certain zone do not react

[crash5937]

Title: Blocks in a certain zone do not react

Version: 0.5.1

OS: Windows 8

Java Version: (build 1.7.0_10-b18)

Description of Problem:

At first, I need to say, that I have Forestry 2.0.0.10 installed, although there are no Forestry blocks in the affected area. If it makes any difference (I think it doesn't, but I don't fully understand the internal mechanics of this modpack and Forge), this problem is on a multiplayer server that I host.

My problem is that a certain area (I'm not really sure if that area is a few chunks, but I think that the borders aren't really chunk borders, as you can see at the minimap in the video that I'll link to below) has blocks, that do not react to mining or any other kind of interaction. Same thing goes with doors - they seem to open, but you can't go through them. Chests do not react and IC machines do not work.

I made a short video of the problem -

- at the end of the video, you can see a hole after a creeper explosion - even though it exploded partly in the affected area, it made the blocks react, so there apparently is a way to make the blocks react. Do you possibly have any solutions? Any ideas what might have caused this? The last thing I did before noticing this bug was building a multiblock farm from Forestry, but it isn't in the affected area.

Error Messages:

Error Log: