Bug Really odd combination of mods crash

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Well-Known Member
Jan 2, 2013
The Netherlands
So I've been having this issue with FastCraft, where it causes my computer to lock-up. This happens in Infinity evolved skyblock as well, so I need to disable FastCraft before I can play it. (annoyingly, the FTB launcher doesn't allow me to download the pack without immediately launching it before I can disable it)

However, I also have this other pack/minecraft-instance, a collection of mods I assembled for myself. And it has FastCraft and doesn't have this problem. But when I created a new pack with less mods than my old pack it does give problems. Fastcraft also gives problems in Regrowth, but at least that pack doesn't include it by default.

Today I decided to wrestle with this problem some more and figure out what is going on. Here is my conclusion;

First, let me explain the problem:
After lanching the game, and after the forge screen goes away and the main menu appears, my computer freezes. The only thing I am able to do is move the cursor around. I can't switch to the desktop, I can't interact with any GUI element and I can't quit the application. Not even the keystrokes that should force-quit the app work.
The only way I can get out of this I by hitting the hard reboot button on my computer case.

No crash log is generated. The logs simply end the moment the lock-up happens, but don't record anything about the lock-up.

After much testing and rebooting my computer I've found the following:

If I don't include thaumcraft, fastcraft doesn't cause problems with any mod.
If I don't include fastcraft, thaumcraft doesn't cause problems with any mod.

So this means fastcraft and thaumcraft don't work together, right, rigth?
Except, my old modpack has both fastcraft and thaumcraft, and it doesn't have any problems!?

So then I decided to test taking away mods from my old pack. And after more testing and rebooting I found the following:

If the pack includes both mystcraft and looking glass, then fastcraft and thaumcraft don't cause any problems together.

I really don't understand this. I also don't understand how this can cause my computer to lock up. The lock-up happens even when minecraft is launching in the background. I thought it was impossible for modern operating systems to lock-up like that.