STEPS TO REPRODUCE
1. Launch iClone 6
2. Apply a project using billboards
3. Go to Menu > Edit > Preference, check the box for "Level of Detail"
4. Click Render Scene on Toolbar, export to Indigo

ACTUAL RESULT
The billboards disappeared in Indigo

EXPECTED RESULT
The result of export to Indigo should be the same as the result of iClone 6 Export