IE vs FF Ajax XmlHttp problem

Hello, I'd like to ask you guys for an advice. Got this function to request some sentences from database (using php file with mysql_query(SELECT *...) stuff, then echoing the result and passing as a parameter to function displaySent(oXHR.responseText, select_sent) - which displays this text using some parsing procedure into the <select> component )
My problem is, that it works without any problems with FF, but in IE it displays only first row in the <select> component...even if i have 5 records in the database, IE displays only first one. XmlHttp request function gets the text string in following form: "sentenceOneStringEnglish#$%sentenceOneStringCzech@@@sentenceTwoStringEnglish#$%sentenceTwoStringCzech". this is being done by concatenation the records from database using "while" loop and adding "@@@" after each record.
I'd be happy for any idea, about where the problem could be.
Thanks

function requestSentences(select_lect, select_sent){	
var id = document.getElementById(select_lect).value;		
var oXHR = zXmlHttp.createRequest();			
oXHR.open("get", "./include_ucitel/ajaxLekcia.php?id_lect_sentences=" + id, true);
oXHR.onreadystatechange = function (){			
    if (oXHR.readyState == 4) {					
	if (oXHR.status == 200 || oXHR.status == 304) {					
            displaySent(oXHR.responseText, select_sent);
	}
	else {
	    alert("Vyskytla sa chyba: " + oXHR.statusText);
	}
    }
};
oXHR.send(null);		
}