I was tinkering when you were posting. I got it working using this code:
export_descr_ancillaries.txt
Code:
;------------------------------------------
Ancillary legate_of_tenth
Image roman_official_ancillary.tga
Unique
ExcludeCultures barbarian, carthaginian, eastern, egyptian, greek
Description legate_of_tenth_desc
EffectsDescription legate_of_tenth_effects_desc
Effect MovementPoints 45
Effect Command 3
Effect BattleSurgery 75
Effect TroopMorale 6
export_ancillaries.txt
Code:
{legate_of_tenth} Legate of 10th
{legate_of_tenth_desc}
Legate of 10th
{legate_of_tenth_effects_desc}
Legate of 10th
Not having the entry in export_ancillaries.txt was probably causing your crash. Is it working now?