EI-330-300, thanks for that info, the website said something like "no seats available", but I intuitively guessed it was cancelled!
EI phoned me today (nice touch, instead of vice-versa) and changed our outbound trip okay, no problem. However, because we'd booked to be away for six weeks, they said I should wait until our original outbound flight (EI0141/10) was "officially cancelled", and then call back to amend our return flight MIA/DUB to a week later.
Seems strange to me, but I'll certainly do as EI asked, so hopefully we can get our planned six weeks in the USA.