So it may have been an issue with Citi at one particular bank. Annoying, but unclear if you walked down the street to another bank/atm, you'd have probably been fine.

In Ukraine and Romania, you cannot use HSBC at any bank in the country. Period. As far as I'm concerned, that's absolutely ridiculous (it wouldn't be if they provided prior notice, but since their policy is not to do this, it's unquestionably poor form).

2 ATM cards when traveling are a must.