http://pastebin.com/PTfuca0t
Finally decided to install this after installing a bunch of other mods for the past week, and I get this crash. I have a feeling Im missing something but I dont know or remember what, as this worked fine on my other instances, which probably means it's either a new mod conflicting or a config thing.
Gonna troubleshoot a bit.

Now that I think about it, it could be a forge thing.

It looks like your version of the EnderIO jar is corrupted. Did you tamper with it in any way?

[17:34:53] [Client thread/DEBUG] [FML/]: Identified a mod of type Lcpw/mods/fml/common/Mod; (crazypants.enderio.EnderIO) - loading
[17:34:53] [Client thread/TRACE] [EnderIO/]: Parsed dependency info : [Forge@[10.13.4.1448,), endercore@[1.7.10-0.2.0.31_beta,)] [Forge@[10.13.4.1448,), endercore@[1.7.10-0.2.0.31_beta,), MineFactoryReloaded, Waila@[1.5.10,), Thaumcraft, appliedenergistics2@[rv2-beta-8,)] []
[17:34:53] [Client thread/ERROR] [FML/]: Unable to read a class file correctly
java.io.EOFException: Unexpected end of ZLIB input stream

Could you have a look into your logfile to see if the stacktrace is longer there? The part that is not following "Caused by: java.lang.ArrayIndexOutOfBoundsException" would be very interesting...

http://pastebin.com/MnZ9KiC5
Im not exactly sure what Im looking for, I did remove all mods except this and Thermal E/F/D, and still got the crash, but I just realized I didnt try one more configuration.

Also, somewhat obviously, the non beta works just fine.

Interesting development, to say the least.
Okay, so I downgraded to the last stable non beta version, It worked.
I then realized that I still had liteloader, so I removed that, but added all my mods + the beta .422
It worked
I took it a step further and just re-enabled Liteloader. It worked.

However, the .422 beta wasnt the one I just downloaded from curse, but an older version of the same file I had from my older instance. (only a month or two old)

So, I have a three theories,
first is that the older version of .422 is different from this latest version, which I'd doubt.
I had to load up some kind of config file for it to continue loading.
Or because I had endercore in the 1.7.10 folder instead of the main mod folder (I like keeping "Core" like mods in there)

As, everything is exactly the same as to when I started trying to load the first time.
Newest forge, Liteloader, all the mods I had already installed. The only thing different is moving endercore and the "old" version.

there is liteloader present and you are using multimc ... try maybe after removing liteloader and finally again with just forge
i bet it's liteloader :P

I dont remember If I did, but I dont think so. Maybe I messed up the download?

Yes, "Unexpected end of ZLIB input stream" usually means the download stopped before the file was transferred completely.

Mind, if you actually read what I wrote it wasnt liteloader.

And Henry, I think that might have been it, but I downloaded it a week ago so I dont really know if I can confirm.
Anyway, no problems anymore. Thanks for trying.

@Fortist turns out my server's HDD was filled up with jenkins logs thanks to a bug. I've resolved the issue so downloads should work fine now.