Well There's Your Problem
The errors about Thermal Expansion and Thaumcraft are just other mods looking for the Thaumcraft API and finding the mod not present. Those can probably be ignored.
As for why the world hangs... How much RAM are you giving Minecraft? I never got Resurrection to load on less than 3GB... and I don't think Resurrection ever really worked right anyway.
Another idea: Do you still have Railcraft installed? If so, try this: Open the Railcraft .jar file, and delete the thaumcraft folder from it. Because that might be doing something it's not supposed to, particularly because you don't have Thaumcraft actually installed.
Thanks for the quick reply!
I allocated 2.5 GB which worked well before updating (although GT5U is 4 or so MB more than normal GT5, so maybe it makes enough of a difference?). According to the F3 info, Used Memory was ~30-50% and Allocated Memory was 50-80% IIRC.
UPDATE: I tried setting it to 3.5 GB, still same thing
As for Railcraft, I have it disabled but I didn't mess around with the files. I'll try that and see if it helps.
UPDATE: This didn't seem to change anything unfortunately.
I also want to add that I'm running the newest version of forge 1.7.10 (1614), if that makes a difference.
I'll try to launch with only IC2 and gregtech installed now.
UPDATE: Success! I did get some scary errors about missing GT textures though. I'll try running it with all the mods I usually have minus CustomOreGen, as I didn't need that to launch and create a world. I hope it won't cause problems.
UPDATE: Nope, same problem as before. Do you know which mod could be causing this freeze?
(Sorry for taking so long to reply, it takes a while for FTB to load up)