Hi,
You can definitely input negative values on any numeric fields ( int, float, vector components, etc). what is your character made of in terms of components?
GetDistance. Are you sure you have all the fields properly filled out? if the gameObject or the target or the storeResult is null, then it will nto work. so it could work on start, but then for example the target was deleted and doesn't exists anymore. Could it be something like that?
bye,
Jean