I've turned off all mods, then activated pyrawores and the mods it depends on. On loading the game, I get this error:
4.968 Mods to disable:Failed to load mods: Error in assignID: item with name 'lead-container' does not exist.
Source: casting-lead-container (recipe).
Installing pyhightech fixed the crash for me.
A similar crash has already been reported for pyalienlife, just with another item ("silicon" instead of "lead-container"); this has also been fixed by adding pyhightech. I believe this happens because pyalienlife pulls in pyrawores (which needs stuff from pyhightech), but neither mod depends on pyhightech.