[Zope] 'id' an ilegal folder name?

Hi, I've created a folder for each country with the 2 letter country code as the folder name. However I keep getting an error with Indonesia - country code 'id'. Given it's use across Zope - is these a reserved word and thus can't be used for naming - or just an edge case no one has encountered before? (I'm using Zope 2.7.x with Plone 2.0.4) Cheers, Duane