Oh god, what have I done...

[neiromaru]

I was using my mining laser's explosive mode to add some random destruction to some ruins I was building when suddenly my game went crazy.
The UI is missing/misplaced, I can't see the server chat or the escape menu. My inventory only shows up sometimes, and lacks the background UI. Item's I hold in my hand are very glitchy, with their geometry appearing in weird places around me.
My console is getting rapidly spammed with an error message as seen in the screenshot below. I can't copy and paste it out because the console window also seems to freeze up.
The damage appears to be limited to the server I play on, singleplayer works fine.

I've tried relogging, restarting my computer, and reinstalling FTB but it's still messed up.

I'm holding a MPS power fist in this screenshot...

 

[SonOfABirch]

lol you done goofed

 

[Vtecem]

I'd post in the support thread.

That said, you could try a fresh install and move your save files over.

Failing that, maybe make a save in NEI of your items and then rename or delete your player.dat file.

 

[Kitchen_Fire]

Wait... The game is not supposed to look this way??

 

[Democretes]

Remember what stuff you had and reset your player.dat file. You'll lose your stuff but that should fix your GUI problem.

 

[matpower123]

This happened to with my friend,also he stupid placed the buggy MPS part(in case the MPS Helmet) and we had to reset his chunk.
Just delete the MPS Helmet and the power glove and it should fix it.

 

[Painstouch]

Forge Backup could help you with that with ease. If you had one!

GL!

 

[neiromaru]

I managed to fix it, here's how in case anyone else runs into this:
I managed to separate all my stuff into a bunch of chests (which involved lots of blindly clicking on broken UIs). Then had a server admin delete my player.dat file. I went through each chest until I found one started bugging things out when I opened it. There were several items in it called "unnamed" with their tooltips appearing way off on the edge of the screen. So, I built a lava pit under the chest and broke it.
My theory is that using explosions to clear microblocks may have caused them to drop as the data that defines what a block space with multiple microblocks in it looks like, and trying to render those outside of the game grid broke the game's geometry, and resulted in those "unnamed" items in the glitchy chest.