[From my original post on MinecraftForums]

For some reasons IDK, every time I try to open a world or create a new one with Mekanism v8+, I just get returned to the Main Screen, and this appear in the logs:

http://pastebin.com/PtGmuxs8

I cut that part as I found it important ( it's where it can't load the map anymore ).

Seriously, editing made it a duplicate on github. But, no spam, I swear!

Pull out AE2 and see if it works. That's an older version of AE2 as well...the newer one won't work yet either so don't put in beta-14...

Update to Mekanism 8.0.1. This has already been fixed.

EDIT:
My bad, that is 8.0.1. That crash doesn't make sense in context.

Fixed

Hum, where I can pick the fix ( or is it a hotfix that didn't change the version ) ?

Gonna test anyways!

Just curious, what is it so you guys have special AE2 compatibility ( because AE2 Spatial-Compat Addon works with both AE2 rv1 and rv2 ) ?

Ok, I guess it's a hotfix, because I can't download it now...

Just shows that strange message when skipping adf.ly:
http://pastebin.com/qRRN4uPy

PS: Any of the three parts.