Wow, that's going to be one damn fine capital!
It looks like his font file got hosed. The odd thing is that the Great Person icon is missing at the top of the first screenshot (GPP Bar), yet it is clearly visible on the CDA in the second screenshot.
Could you please have him try a few things and report back?
- Switch to another language.
- Rename the font file "CustomAssets/Res/Fonts/GameFont_75.tga" to something else (e.g. add ".old") and restart Civ.
- Uninstall and reinstall BUG. Try it as a mod if he's currently using it in CustomAssets.
- Does he have any other mods installed, e.g. BlueMarble?
- Is he using CivScale to change his fonts?
- Verify that the normal game without BUG works fine.
This is gonna be a fun one!
Absolutely not. BUG should work fine with both 3.13 and 3.17. I'm still using 3.13 myself.