I have a geometric network in a file geodatabase and the first time I used the domains after making them they worked. The next time I was in the project all domains stopped working. I tried everything--removing the domains from the fields, deleting the domains, re-creating them from tables, re-applying them to the same fields...still no luck. I tried them in a fresh mxd too. None of them are on a subtype field, all are appropriate data types for the fields they are assigned to (just to head off a few questions).
It is weird they worked at first than just stopped working. Is this a known bug, perhaps some kind of incompatibility with feature classes in a geometric network? I have never had attribute domains just stop working like this before.