Colliders reading tags as Untagged

Unity 3.4 was crashing just every few minutes on Win 7, so I jumped
at the chance to upgrade to 3.4.1.

It doesn’t crash quite as often now, and everything I did in 3.4 still works.
(…it now crashes several times a day instead of several times an hour.)

The problem I’m having now, is that any new collider that was added with 3.4.1
reads all tags as “Untagged”, while the old 3.4 colliders still read the tags properly.
(Type of collider doesn’t seem to matter)

Any ideas?

Thanks in advance.

var explosion : Transform;
private var clone : Transform;

function OnCollisionEnter (other : Collision)
	if(other.gameObject.tag == "PlayerAmmo" || other.gameObject.tag == "Grenade")
		Destroy (gameObject);
		clone = Instantiate(explosion,
		transform.position, transform.rotation);