Fatal error when I finish research

[FireBladesX]

When I complete an upgrade, the game gives me a fatal error. The upgrade's only effect is the "ability level bonus" effect, and there's only a fatal error if a unit who benefits from the upgrade has died very recently (their corpse is still there). I tried removing the corpse from the unit that benefits from the upgrade (I changed the death options to can't raise, does not decay), but the problem persists.
The ability being upgraded is based off of unholy aura, and there are no triggers associated with the upgrade whatsoever.

Has this happened to anyone before, or does anyone know how to fix the problem?

 

[Varine]

Something to do with the triggers probably. Can you post it?

 

[Weep]

Is the ability in a spellbook? I've had crashes when trying (via triggers) to change the level of an ability within a spellbook for a dead unit.

 

[FireBladesX]

The ability being upgraded is based off of unholy aura, and there are no triggers associated with the upgrade whatsoever.

So yeah, there's no trigger to post. It's an upgrade, made in the object editor.
The affected spell is not a spellbook.