dodo, I know I sowed the seeds of doubt on this one on your previous query. So I went and checked. The US does have a requirement for passports to be valid for six months after your dates of travel but it seems to be waived for some visa waiver countries. Here is an FAQ that applies to Britain:
[broken link removed]
The link to the list of countries for which the same rule is applied seems to include Ireland. So it looks like you're ok. If you want to be 100% sure, you might want to ring the US embassy.