Using mffs_rev5_for_1.2.5-bukkit.zip and I was trying out the Reactor Server/Client, I stuck a Client on the side of a reactor chamber, and my server.log got this error. It basically corrupted my world I think (just a test world).
2012-07-23 18:52:12 [SEVERE] Unexpected exception
java.lang.ClassCastException: mffs.TileEntityReaktorMonitorClient cannot be cast to mffs.TileEntityPassivUpgrade
at mffs.TileEntityReaktorField.checkupgrades(TileEntityReaktorField.java:379)
at mffs.TileEntityProjektor.q_(TileEntityProjektor.java:326)
at net.minecraft.server.World.tickEntities(World.java:1190)
at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:569)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:467)
at net.minecraft.server.ThreadServerApplication.run(SourceFile:492)
Edit:
Also, if I should die and respawn outside the force field... how do you get back inside? I found a sort of cheating way inside... the forcefield cube went through a tree. I got on top of the tree and dug down really fast through the leaves, and I was able to drop down inside of the forcefield before it filled in the blocks where the leaves used to be. So I was able to get back in that time... but not sure how you're supposed to do it in the future.
Edit2:
I'd also add that the force field generator was being powered by some solar arrays, so I don't think I could "wait it out" until the shield failed for me to get back inside. It looks like the other version has some kind of security gates or something? Is that somewhere in this edition? This is kind of like locking your keys inside of your car. I can't figure out how to get back inside.