The file /etc/init.d/irda provided by net-wireless/irda-utils-0.9.16-r1 (current stable version) contains the statement
referring to /etc/init.d/serial that, to the extent of my knowledge, is long gone from baselayout. In any case, the irda service only works on my machine if I comment this statement out.
Err, it's still provided by sys-apps/setserial ebuild for people that need it. Anyway, I don't see why it should fail because of this, it doesn't depend on it, just tells to start after serial has started if it's available in that runlevel.
Reopen with emerge --info.
I think my problem was due to the fact that i still had an old and broken /etc/init.d/serial lying around. I deleted it and now everything works fine. Sorry about the premature bugreport.
OK, thanks for reporting back.