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Ok, at least we can rule out the update being the problem.
Delete your DW20 folder (yes the whole thing)
Let it redownload.
It looks to me like a problem with the configs. But different mods each time.
Make sure you don't have any of the files open when you're trying to run
I did that earlier as well, though I think I noticed something. It opens up once, and if I close it and reopen it, it says that a newer version of the mod pack is available. I downloaded the new version and that one crashed upon opening. Maybe something to do with the newest version of the mod pack?