Many thanks!
I didn't know there were several 1.4 versions out. I updated to 20140901-000000 and the problem was solved.
I've noticed a little issue with Voobly offline recently. If you've installed Voobly, please try the following:
1. browse to your "Age of Empires II\Data" folder
2. look for these 2 files: "empires2_x1_p1.dat" and "empires2_x1_v1.dat"
3. if you have the "v1" but not the "p1", then Voobly may have corrupted the installation
4. to fix this, clone the "empires2_x1_v1.dat" file and rename the clone to "empires2_x1_p1.dat"
5. try the game now
This issue has been reported to them, and hopefully it will be fixed soon. If, on the other hand, you have both files, how did you install the game? Was it from Steam or the retail game CDs?