Just found the data for a working case. The data is inserted inline in the page with it looks like the new picklist
calls wiring the data up to the fields:
<script type="text/javascript">//<![CDATA[
window.pl = window.pl || {};
pl.map_63_012d0000000sh5I={'CA':'JAACAMDk0AEA','US':'2//9/z8bL/4A'};
pl.vals_63_012d0000000sh5I=['AK','AK','AL','AL','AB','Alberta','AZ','Arizona','AR','Arkansas','BC','British Columbia','CA','California','CO','Colorado','CT','Connecticut','DE','Delaware','DC','District of Columbia','FL','Florida','GA','Georgia','HI','Hawaii','ID','Idaho','IL','Illinois','IN','Indiana','IA','Iowa','KS','Kansas','KY','Kentucky','LA','Louisiana','ME','Maine','MB','Manitoba','MD','Maryland','MA','Massachusetts','MI','Michigan','MN','Minnesota','MS','Mississippi','MO','Missouri','MT','Montana','NE','Nebraska','NV','Nevada','NB','New Brunswick','NL','Newfoundland and Labrador','NH','New Hampshire','NJ','New Jersey','NM','New Mexico','NY','New York','NC','North Carolina','ND','North Dakota','NT','Northwest Territories','NS','Nova Scotia','NU','Nunavut','OH','Ohio','OK','Oklahoma','ON','Ontario','OR','Oregon','PA','Pennsylvania','PE','Prince Edward Island','QC','Quebec','RI','Rhode Island','SK','Saskatchewan','SC','South Carolina','SD','South Dakota','TN','Tennessee','TX','Texas','UT','Utah','VT','Vermont','VA','Virginia','WA','Washington','WV','West Virginia','WI','Wisconsin','WY','Wyoming','YT','Yukon Territories'];
pl.noneLabel="--None--";
pl.naLabel="\*\*Not Applicable\*\*";
pl.selectedLabel="Chosen";
pl.availableLabel="Available";
new picklist('policyholder:f:ppb:c:pb:cpbs:Contact-1:Section-1:Contact___MailingStateCode','63_012d0000000sh5I','policyholder:f:ppb:c:pb:cpbs:Contact-1:Section-1:Contact___MailingCountryCode',['',''],' id=\"policyholder:f:ppb:c:pb:cpbs:Contact-1:Section-1:Contact___MailingStateCode\" name=\"policyholder:f:ppb:c:pb:cpbs:Contact-1:Section-1:Contact___MailingStateCode\"',true,true);
new picklist('policyholder:f:ppb:c:pb:cpbs:Contact-1:Section-1:Contact___OtherStateCode','63_012d0000000sh5I','policyholder:f:ppb:c:pb:cpbs:Contact-1:Section-1:Contact___OtherCountryCode',['',''],' id=\"policyholder:f:ppb:c:pb:cpbs:Contact-1:Section-1:Contact___OtherStateCode\" name=\"policyholder:f:ppb:c:pb:cpbs:Contact-1:Section-1:Contact___OtherStateCode\"',true,true);
picklist.initialized = false;
picklist.initAll();
//]]>
...
</script>
Now just have to figure out why that JavaScript doesn't get emitted in the failing page...
PS
The problem turned out to be that one page was set to API 18.0 (the one that didn't work) and the other page was set to API 20.0 (the one that did work). Changing to API 20.0 fixed the problem.
MailingCountryCode
andMailingStateCode
in VF page?