javascript - id, string or integer was expected with eval() -

i strange error in ie.. no problems in both ff , chrome

when alert variable this:

json_post('delete_accounting', 'json.action.php?action=delete_accounting', 'id=682', 'rtn_accounting', {tr_id:'tr_acc682', enc_id:374, delete:1}); 

but when want eval() sting error (the error translated danish, don't know how put in english?)

id, string or integer expected 

edit:

var xmlhttp = {}; function json_post(request_var, response, get_str, callback_function, callback_var) {     request_var += math.floor(math.random()*999).tostring();      cnstr.mouseloader.cnstr();      if(window.xmlhttprequest) xmlhttp[request_var] = new xmlhttprequest();     else if(window.activexobject) xmlhttp[request_var] = new activexobject('microsoft.xmlhttp');      xmlhttp[request_var].open('post', response, true);     xmlhttp[request_var].setrequestheader('content-type', 'application/x-www-form-urlencoded');     xmlhttp[request_var].onreadystatechange = function()     {         if(xmlhttp[request_var].readystate == 4)         {             cnstr.mouseloader.dstr();              if(callback_function) eval(callback_function+'('+xmlhttp[request_var].responsetext+(callback_var ? ', callback_var':'')+')');         }     }     xmlhttp[request_var].send(get_str); } 

i'm quite sure error occurs in eval() because when run sting real code there no problems..

like this:

json_post('delete_accounting', 'json.action.php?action=delete_accounting', 'id=682', 'rtn_accounting', {tr_id:'tr_acc682', enc_id:374, delete:1}); 

i have tried escape in callback function rtn_accounting(), , still same error in same line eval()

by adding quotes in object in last parameter works

json_post('delete_accounting', 'json.action.php?action=delete_accounting', 'id=682', 'rtn_accounting', {'tr_id':'tr_acc682', 'enc_id':374, 'delete':1});