The Invasion CB shouldn't really cause any issues, yeah.
Do you have the save perhaps? If I can replicate it then I should at least be able to figure out what part of the code causes the crash, and then depending on the cause either fix it or report it to Paradox.
My save is attached, the only other thing I'm afraid of now is if my computer isn't up to snuff or something. It should crash on forcing my demands on Novgorod or before the end of the month if my character is left to the AI. Thanks again for having look.
http://filesmelt.com/dl/Mongol_Empire1292_05_21.ck2