A new turn happened adn one of the AI casts a spell which crashed the game. It also had weird verticle bars. I report this to someone and does anyone know what happened?

I can still move the cursor, but everything is frozen

That's a known bug, never managed to find a proper way to fix it because it's impossible to reproduce.
About once every few dozen times, clicking on a global enchantment window too quickly crashes the game.

Thank you! I wonder what could be causing this.

Memory corruption is the only thing that can cause it. The fact that moving the mouse still moves the cursor means that the game did not crash, it's just stuck in an infinite loop. It also means that this did not occur during a page flip, as cursor drawing is disabled then. Therefore, the glitch lines you see on the screen were not meant to be drawn there - they were meant to be drawn into the page used to compose the next frame. But once you click away the global enchantment notification, the next draw happens exclusively from EMS handles, which excludes the usual memory deallocation issue (trying to draw from a buffer that's no longer there). Coupled with the frequency (personally, I've never seen this in 25 years), and being unable to reproduce the bug, I don't really see any other viable explanation. But if I can think of one, I'll try to track it down.