I became aware of the problem yesterday evening thanks to a post on Boards.ie*. The poster had been wanting to view FindMyPast.ie's indexes to the National Library of Ireland's collection of RC parish registers but was being denied access and prompted to take out a subscription. (While the indexes can be accessed on Ancestry only via subscription, they are supposed to be free on FindMyPast, provided the researcher has a free registered account.)
Strangely, these indexes were correctly free to access via FindMyPast.co.uk (here).
This morning FindMyPast has tweeted the following in reply to my contact last night:
Their reply could seem to suggest that other collections or FMP sites may be affected.
*In my opinion, the best free forum for Irish genealogists.
UPDATE, 26 July, 12:30: FindMyPast has confirmed that the technical error has been corrected and the free records should once again be free to access with a free registered account.