In my Superflat world, I have a Nuclear Reactor. But, when I check it to see how it's doing, I get a massive lag spike (5 FPS) and I have to reload Minecraft to remove it. But something's very weird - if the reactor performs the bug where no sound is playing, I don't get the lag. It seems pretty weird.
I'm using
The latest 1.2.5 version of Modloader
The 3.1.3.105 version of Forge
With the following IC2 plugins:
Modular Force Field System
Compact Solars
Advanced Machines
I would be very thankful if someone can help me out. 