Uh, that could all be a collection of the most questionable things to do all in one session, hahahahahahaha!
Wow, Zero, taahahaha, man. Well, don't know where to start. Jeeez, the most mysterious things are png imports, because png is a wild format, really. It's like somebody sort of handed out an idea for what a format could be like and went:" Just sorta do it kinda like that way and call it ".png", if you will!". Photoshop's pngs, especially with alpha, can be naughty ones and my import is likely the most rudimentary there is. So that alone can cause some strange things to happen. Let alone image brushes that are imported that way is already a wild card, because I have not written that conversion and remember it causing troubles before. But also, when you do a big save like that, it is a bit risky to switch to any other app that uses GL and Browsers most certainly do. So this could corrupt the GPU memory in a flash.
As a general precaution I would recommend not switching tasks while you are saving. Just get something from the fridge in the meantime or so, hahaha...at such resolutions saving can take time.
I should make it my goal to get you out of photoshop, hahaha, because it just can't be that Verve won't give you all you need. Someday you'll have to tell me what you're missing and why you go to photoshop exactly and I'll see what I can do, I promise!
I do believe that this was a system related crash for now. You can always send me your brushes and swatches just out of curiosity. Who knows, maybe there is something funky I can track down that way?!
But ABOVE ALL, Zero, THANK YOU for going through all this with me, this is great feedback and a great spirit! Ich mag auch, dass Du mal kurz auf Deutsch umgesprungen bist, hahaha, sehr witzig!