var selektion;

function insertAtCursor(myField, myValue, bbCode1, bbCode2, endOfLine) {
var bbb;
if(bbCode1=='[url=null]') { bbCode1=''; bbCode2=''; }
if(bbCode1=='[imgs]' && myValue==null) { bbCode1=''; bbCode2=''; myValue=''; }
if(bbCode1=='[imgs=null]') { bbCode1=''; bbCode2=''; myValue=''; }
if(bbCode2=='null[/imgs]') { bbCode2='[/imgs]'; myValue=''; }

//MOZILLA/NETSCAPE/OPERA support
if (typeof(myField.selectionStart) == 'number') {
var startPos = myField.selectionStart;
var endPos = myField.selectionEnd;
var scrollTop = myField.scrollTop;
var bbb2, bbV, eoll;
if(myValue=='') myValue = myField.value.substring(startPos, endPos);
//alert(myValue);
myField.value = myField.value.substring(0, startPos) + bbCode1 + myValue + bbCode2 + endOfLine + myField.value.substring(endPos, myField.value.length);
if(myValue=='') {

if(bbCode1.substring(0,4)=='[img' ){
bbb=bbCode1.length + myValue.length + bbCode2.length;
myField.selectionStart=startPos+bbb; myField.selectionEnd=startPos+bbb;
}
else{
bbb=bbCode1.length;
myField.selectionStart=startPos+bbb;
myField.selectionEnd=endPos+bbb;
}

}
else {
bbb=bbCode1.length;
bbb2=bbCode2.length;
bbV=myValue.length;
eoll=endOfLine.length;
myField.selectionStart=startPos+bbV+bbb+bbb2+eoll;
myField.selectionEnd=myField.selectionStart;
}
myField.focus();
myField.scrollTop = scrollTop;
return;
}

else if (document.selection) {
//IE support
var str = document.selection.createRange().text;
myField.focus();
sel = document.selection.createRange();
sel.text = bbCode1 + myValue + bbCode2 + endOfLine;
if(myValue=='') {
bbb=bbCode2.length; 
if(bbCode1.substring(0,4)=='[img' ) bbb=0; else bbb=-bbb;
sel.moveStart('character',bbb); sel.moveEnd('character',bbb);
}
sel.select();
return;
}

else {
myField.value += myValue;
return;
}
}

function paste_strinL(strinL, isQuote, bbCode1, bbCode2, endOfLine, User){ 
if((isQuote==1 || isQuote==2) && strinL=='') alert(l_quoteMsgAlert);
else{
if (isQuote==1) {
bbCode1='[quote=' + User + ']'; bbCode2='[/quote]'; endOfLine='\n';
}
if (isQuote==2) {
bbCode1='[b]'; bbCode2='[/b]'; endOfLine='\n';
}
var isForm=document.getElementById('postMsg');
if (isForm) {
var input=document.getElementById('postText');
//var input=document.forms["postMsg"].elements["postText"];
insertAtCursor(input, strinL, bbCode1, bbCode2, endOfLine);
}
else alert(l_accessDenied);
}
}

function pasteSel() {
selektion='';
if(window.getSelection) {
this.thisSel=window.getSelection()+'';
selektion=this.thisSel.toString();
}
else if(document.getSelection) selektion=document.getSelection()+'';
else if(document.selection) selektion=document.selection.createRange().text;
}


function trimTxt(s) {
while (s.substring(0,1) == ' ') {
s = s.substring(1,s.length);
}
while (s.substring(s.length-1,s.length) == ' ') {
s = s.substring(0,s.length-1);
}
return s;
}
<!--FUNCION IMPORTANTE DONDE SE EXAMINA EL CONTENIDO DE LOS POST
function submitForm(){

var pf=document.forms['postMsg'];
var ftitle=false, ftext=false, flogin=false, fpass=false, user_usr='', user_pwd='', topicTitle='', postText='', fsubmit=true;
if(pf.elements['user_usr']) { flogin=true; user_usr=trimTxt(pf.elements['user_usr'].value); }
if(pf.elements['user_pwd']) { fpass=true; user_pwd=trimTxt(pf.elements['user_pwd'].value); }
if(pf.elements['postText']) { ftext=true; postText=trimTxt(pf.elements['postText'].value); }
if(pf.elements['topicTitle']) { ftitle=true; topicTitle=trimTxt(pf.elements['topicTitle'].value); }
if(pf.elements['CheckSendMail'] && pf.elements['CheckSendMail'].checked) { tlength=0; }
<!--LOS SIGUIENTES IF COMPRUEBAN USUARIOS CONTRASEŅAS
if(flogin && fpass && user_usr!='' && user_pwd!='') fsubmit=true;
else if(flogin && fpass && anonPost==0 && user_pwd=='') fsubmit=false;
<!--en la siguiente linea modifique el valor del fsubmit a true porq con el tinymce se activaba y se ponia a false lo que producia que no dejara la insercion del post en la base de datos
else if(ftext && postText.length<tlength) fsubmit=true;
else if(ftitle && topicTitle.length<tlength) fsubmit=false;

<!--este if es el encargado de controlar los permisos de los usuarios.si fsubmit es false salta la alerta de "el usuario no tieme permisos" si es true mete la informacion de la textarea en la base de datos.(aqui empieza el error cuando integro el tinymce)

if(fsubmit) { pf.elements['subbut'].disabled=true; document.forms['postMsg'].submit(); } 
else { alert(l_accessDenied); return; }
}