Infolog shows version 451. I had this bug myself - new engine versions don't cause truoble, but sometimes ZKL launches old versions that still have the bug - missions in particular are a possible source.
You can work around it by deleting your cache before you play.
Delete everything in C:\Users\[username]\Documents\My Games\Spring\cache\98dev-develop
before you play. Your boot-up will still be long as your computer recomputes things, but it will work until the problem is fixed properly.