Question: What mod (or prerequesite) is messing with my SMP server?

I understand this isn't a general minecraft support forum, but I wanted to post it in here because I think it has to do with one of the prerequisite mods for IC2. Here are the problems we are having the most current version of IC2 (1.90):
-It is impossible to place buttons, switches, vines, or similar objects (except ladders) on the sides of blocks, with certain exceptions. This is extremely frustrating and severely impacting our redstone experimentation. We like to build roleplay dungeons/adventures and this makes it nearly impossible to do.
-Jetpacks are no longer working (again). You can fly, but the fuel never depletes, and fall damage accumulates with your downward travel in the air. AKA a 1 minute flight equals exploding into little bits upon landing. Additionally, it seems like we cannot activate hover mode (although other items using modes work great). Also, you can fly almost absurdly high with the electric packs now (roughly height 180). We've gotten so fed up with this that we have given up on jetpacks on SMP unless we are going straight up.
Minor issues:
-Rarely, all the faces of ALL IC2 blocks rotate. This happens very often on windmills individually.
-Having a fair amount of wiring in view seems to drop frame rates quite a bit. Not sure why, they are just rectangles.

I've looked at Modloader, ModloaderMP, and Forge's release notes and known issues but none of them have addressed these problems. Are these all related to vanilla Minecraft then?

FYI, here is a list of my current mods:
Modloader 1.2.4, ModloaderMP 1.2.4V1, MCForge 2.0.0.67
SoundModEnabler
TooManyItems 1.2.4
Plasmacraft 0.2.8
TwilightForest 1.7.2
Industrialcraft 1.9.0

Thanks for the reply, Richard. I'll try removing Plasmacraft from the server and seeing if that changes anything.

For 4, I'm not sure if this is appropriate use of cables, but I had 3 40-block-long 4x-insulated HV-cables that ran adjacent to one another. I painted all 3 wires so they were completely separate. My fps dropped from 70 to 45 while looking at them. Not sure if it was the cables themselves or some weird situation I had wired. The cables were not yet connected to anything.

Update: Plasmacraft was the obnoxious one disabling my ability to place buttons, etc. Props to you Richard for nailing the diagnosis. Our MC quality of life is greatly improved!