What is wrong in my code?

Works fine for me...
My guess is that at some point you've used a non-standard quotes (probably because you're using the French keyboard settings), and Acrobat does not like that.

Thanks Try67.

I replaced all accentued character by their Unicode code and remove all comas inside items : it works fine now !

;-)

Here is my new code :

var reply = app.popUpMenu(["A","AFGHANISTAN","AFRIQUE DU SUD","\u00C5LAND \(\u00CELES\)","ALBANIE","ALG\u00C9RIE","ALLEMAGNE","ANDORRE","ANGOLA","ANGUILLA","ANTARCTIQUE","ANTIGUA-ET-BARBUDA","ARABIE SAOUDITE","ARGENTINE","ARM\u00C9NIE","ARUBA","AUSTRALIE","AUTRICHE","AZERBA\u00CFDJAN"],["B","BAHAMAS","BAHRE\u00CFN","BANGLADESH","BARBADE","B\u00C9LARUS","BELGIQUE","BELIZE","B\u00C9NIN","BERMUDES","BHOUTAN","BOLIVIE \(\u00C9TAT PLURINATIONAL DE\)","BONAIRE \(SAINT-EUSTACHE ET SABA\)","BOSNIE-HERZ\u00C9GOVINE","BOTSWANA","BOUVET \(\u00CELE\)","BR\u00C9SIL","BRUNEI DARUSSALAM","BULGARIE","BURKINA FASO","BURUNDI"],["C","CA\u00CFMANS \(\u00CELES\)","CAMBODGE","CAMEROUN","CANADA","CAP-VERT","CENTRAFRICAINE \(R\u00C9PUBLIQUE\)","CHILI","CHINE","CHRISTMAS \(\u00CELE\)","CHYPRE","COCOS \(\u00CELES\)","COLOMBIE","COMORES","CONGO","CONGO \(R\u00C9PUBLIQUE D\u00C9MOCRATIQUE DU\)","COOK \(\u00CELES\)","COR\u00C9E \(R\u00C9PUBLIQUE DE\)","COR\u00C9E \(R\u00C9PUBLIQUE POPULAIRE D\u00C9MOCRATIQUE DE\)","COSTA RICA","CÔTE D’IVOIRE","CROATIE","CUBA","CURAÇAO"],["D","DANEMARK","DJIBOUTI","DOMINICAINE \(R\u00C9PUBLIQUE\)","DOMINIQUE"],["E","\u00C9GYPTE","EL SALVADOR","\u00C9MIRATS-ARABES-UNIS","\u00C9QUATEUR","\u00C9RYTHR\u00C9E","ESPAGNE","ESTONIE","\u00C9TATS-UNIS","\u00C9THIOPIE"],["F","FALKLAND \(\u00CELES\)","F\u00C9RO\u00C9 \(\u00CELES\)","FIDJI","FINLANDE","FRANCE"],["G","GABON","GAMBIE","G\u00C9ORGIE","G\u00C9ORGIE-DU-SUD ET LES \u00CELES SANDWICH-DU-SUD","GHANA","GIBRALTAR","GR\u00C8CE","GRENADE","GROENLAND","GUADELOUPE","GUAM","GUATEMALA","GUERNESEY","GUIN\u00C9E","GUIN\u00C9E-BISSAU","GUIN\u00C9E \u00C9QUATORIALE","GUYANA","GUYANE FRANÇAISE"],["H","HA\u00CFTI","HEARD ET \u00CELES MACDONALD","HONDURAS","HONG-KONG","HONGRIE"],["I","\u00CELE DE MAN","\u00CELES MINEURES \(\u00C9LOIGN\u00C9ES DES \u00C9TATS-UNIS\)","\u00CELES VIERGES \(UK\)","\u00CELES VIERGES \(USA\)","INDE","INDON\u00C9SIE","IRAN \(R\u00C9PUBLIQUE ISLAMIQUE DE\)","IRAQ","IRLANDE","ISLANDE","ISRA\u00CBL","ITALIE"],["J","JAMA\u00CFQUE","JAPON","JERSEY","JORDANIE"],["K","KAZAKHSTAN","KENYA","KIRGHIZISTAN","KIRIBATI","KOWE\u00CFT"],["L","LAOS \(R\u00C9PUBLIQUE D\u00C9MOCRATIQUE POPULAIRE\)","LESOTHO","LETTONIE","LIBAN","LIB\u00C9RIA","LIBYENNE \(JAMAHIRIYA ARABE\)","LIECHTENSTEIN","LITUANIE","LUXEMBOURG"],["M","MACAO","MAC\u00C9DOINE \(EX-R\u00C9PUBLIQUE YOUGOSLAVE DE\)","MADAGASCAR","MALAISIE","MALAWI","MALDIVES","MALI","MALTE","MARIANNES DU NORD \(\u00CELES\)","MAROC","MARSHALL \(\u00CELES)","MARTINIQUE","MAURICE","MAURITANIE","MAYOTTE","MEXIQUE","MICRON\u00C9SIE \(\u00C9TATS F\u00C9D\u00C9R\u00C9S DE\)","MOLDOVA \(R\u00C9PUBLIQUE DE\)","MONACO","MONGOLIE","MONT\u00C9N\u00C9GRO","MONTSERRAT","MOZAMBIQUE","MYANMAR"],["N","NAMIBIE","NAURU","N\u00C9PAL","NICARAGUA","NIGER","NIG\u00C9RIA","NIU\u00C9","NORFOLK \(\u00CELE\)","NORV\u00C8GE","NOUVELLE-CAL\u00C9DONIE","NOUVELLE-Z\u00C9LANDE"],["O","OC\u00C9AN INDIEN \(TERRITOIRE BRITANNIQUE DE\)","OMAN","OUGANDA","OUZB\u00C9KISTAN"],["P","PAKISTAN","PALAOS","PALESTINIEN \(TERRITOIRE OCCUP\u00C9)","PANAMA","PAPOUASIE-NOUVELLE-GUIN\u00C9E","PARAGUAY","PAYS-BAS","P\u00C9ROU","PHILIPPINES","PITCAIRN","POLOGNE","POLYN\u00C9SIE FRANÇAISE","PORTO RICO","PORTUGAL"],["Q","QATAR"],["R","R\u00C9UNION","ROUMANIE","ROYAUME-UNI","RUSSIE \(F\u00C9D\u00C9RATION DE\)","RWANDA"],["S","SAHARA OCCIDENTAL","SAINT-BARTH\u00C9LEMY","SAINTE-H\u00C9L\u00C8NE \(ASCENSION ET TRISTAN-DA-CUNHA\)","SAINTE-LUCIE","SAINT-KITTS ET NEVIS","SAINT-MARIN","SAINT-MARTIN - FR","SAINT-MARTIN - NL","SAINT-PIERRE-ET-MIQUELON","SAINT-SI\u00C8GE - \(\u00C9TAT DE LA CIT\u00C9 DU VATICAN\)","SAINT-VINCENT ET LES GRENADINES","SALOMON \(\u00CELES\)","SAMOA","SAMOA AM\u00C9RICAINES","SAO-TOM\u00C9 ET PRINCIPE","S\u00C9N\u00C9GAL","SERBIE","SEYCHELLES","SIERRA LEONE","SINGAPOUR","SLOVAQUIE","SLOV\u00C9NIE","SOMALIE","SOUDAN","SOUDAN DU SUD","SRI LANKA","SU\u00C8DE","SUISSE","SURINAME","SVALBARD ET \u00CELE JAN MAYEN","SWAZILAND","SYRIENNE \(R\u00C9PUBLIQUE ARABE\)"],["T","TADJIKISTAN","TA\u00CFWAN \(PROVINCE DE CHINE\)","TANZANIE \(R\u00C9PUBLIQUE UNIE DE\)","TCHAD","TCH\u00C8QUE \(R\u00C9PUBLIQUE\)","TERRES AUSTRALES FRANÇAISES","THA\u00CFLANDE","TIMOR-LESTE","TOGO","TOKELAU","TONGA","TRINIT\u00C9-ET-TOBAGO","TUNISIE","TURKM\u00C9NISTAN","TURKS-ET-CA\u00CFCOS \(\u00CELES\)","TURQUIE","TUVALU"],["U","UKRAINE","URUGUAY"],["V","VANUATU","V\u00C9N\u00C9ZUELA \(R\u00C9PUBLIQUE BOLIVARIENNE DU\)","VIET NAM"],["W","WALLIS ET FUTUNA"],["Y","Y\u00C9MEN"],["Z","ZAMBIE","ZIMBABWE"]);if (reply!=null) {event.target.value = reply;}

That's good, although the original code you posted worked for me as well...

Yes, it works on the Windows version of Acrobat 10.1.1, but not on my Mac version…
:-(