I just had an experience in the UK with my Chase ATM card being rejected. Upon arriving home, I listened to my voicemail, and had 2 messages from the fraud department indicating irregular usage (or attempted usage, as I never was able to get cash). I called and pointed out that I had told them in advance to flag my account for overseas usage (which they acknowledged), but they still blocked me from using my ATM card.

Moral of the story, as stated before -- have a backup source of cash...