I've spoken to the author of the Dungeons 2 mod about this issue, but he's pointed me in your direction. Apologies if this is wasting your time, if it's not RC.

https://pastebin.com/D3ajWrPr

Haha what the fuck.. That is indeed ReC, in a way... But that doesn't look right. A String that's too long for the VM to handle?

Can you tell me what you were doing?

Um.. I have no idea. I've been getting this bug where I can't place blocks, trees, whatever. I think it's also related to Cyclic 1.7.8 but I can't narrow it down specifically - it seems a combination of several mods is causing this weirdness.

It looks more like your VM settings are off in general. Perhaps it's got something to do with the launcher? Any update on this?

I've gotten this several times with various combinations of mods. It seems to be completely random as to when it occurs. I'm thinking that sometimes the poem generator fails to set an exit condition, and just keeps looping and chewing up RAM while generating a poem.