The National Library of Ireland has confirmed that its Roman Catholic Parish Registers collection is currently offline due to a technical problem. This may or may not be the same problem that was causing intermittent loss of access earlier in the week, which seemed to have been corrected.
The techies are working on it and hope to restore access soon.
I'll update here, as and when.
Update, 7pm: Site is back up and running, but it carries a message saying: 'Please note: that due to maintenance a small number of registers are currently unavailable.'
Update, 12 January: See advance warning of site being offline on Monday 15 January.