>I finally managed to hack things into enough pieces to avoid the error. What I don't understand is how it ever compiled previously...

Maybe it didn't. I remember from my first job in the US, when I was given a problem in the shape of "this thing doesn't work for this customer"... I'd look into it, then ask "how did this work last year?" (it was a seasonal app). It didn't. Then "how does this work for other customers?". It doesn't. It never worked. Happened several times.