Why would CopyEntity() return an invalid entity?

I haven't had sleep in a day or two, so this may be something really stupid, but why would CopyEntity() return a handle to an entity and then any Entity command I use on that handle give me an "entity does not exist" error?

This code sample shows what I mean, I guess

PositionEntity t\sprite,10,10,10
p\sprite=CopyEntity(t\sprite)
EntityAlpha p\sprite,0.5

So t\sprite must be there, because I position it right before I copy it ( just to prove to myself it was there. )

But EntityAlpha ( or any other entity command on the "supposedly copied" p\sprite errors me with "entity does not exist".

Note, it returns a long integer, just like en entityhandle. It does not return zero.

Probably something stupid, but I'll be damned if I can see it.