OK, I'll play (although old people dying is hardly ironic or curse-like.) Anyway, John Travoltav had a son with a rare disease who died young. I kept thinking about that while watching this.

As a sort of addition to your "number two" point, actor JOHN MEGNAwho plays one of Travolta's classmates(but who may have been best known as the young neighbor kid in "To Kill a Mockingbird") also died from AIDS! I don't know if it would be a stretch or not to surmise that, because "Boy" director RANDAL KLEISER is gay, perhaps quite a few of the cast in his movies might be as well!

Gonna have to do better than that..

Robert Reed died of cancer, although he tested positive for HIV at the time of his death.

Well, I suppose one could argue that it's ironic in that after doing a movie about a boy with an immune deficiency, one would think that everybody on the cast would be extra careful in avoiding getting AIDS because it's an immune deficiency.

It is not ironic that Robert Reed died of a disease of immune deficiency, it is coincidental.

#5: John Travolta ended up acting in crappy movies (coughBATTLEFIELDEARTHcough)

John Travolta became a Scientologist in 1975, a year before of this film.

I wouldn't say Glynnis had no career. Maybe not a superstar career but she's doing OK. She still works and has a movie coming out soon. And she still looks good for someone over 50. Oh, and she was in one of the funniest movies of all time:
Johnny Dangerously

@ #4 - not exactly a curse.. he now makes money off people seeking religious advice.. lol.. smart move imo :P.
As the big sci fi novelist said (loosely): If you want to make real money, you have to start your own religion.