This is extremely high priority. We could use more information.
Next time you get this bug, can you please do the following:
1) Alt-Tab or exit the game
2) in Windows navigate to Dawn of Fantasy installation folder
3) Find Log1.txt file
4) Using the Forum Reply Attachment Manager, upload your log with your reply (you might need to zip or rar it if its over 1.5 Mbs in size)
We would greatly appreciate your help.