Crashing on www method

When I call it inside a IEnumerator:

 WWW www2 = OrganizeData(callParams);

Sometimes the game crashes. Here is the OrganizeData:

  private WWW OrganizeData(string[] callParams)
     {
         string time= GetNonce().ToString();
         WWWForm form = new WWWForm();        
         form.AddField("toTime", time);
 
         for (int i = 0; i < callParams.Length; i += 2)
         {
                 form.AddField(callParams[i], callParams[i + 1]);               
         }
 
         Dictionary<string, string> headers = form.headers;
 
         Encoding encoding = Encoding.UTF8;
         var codeTemp = encoding.GetBytes(code);
 
         using (var hmacsha512 = new HMACSHA512(codeTemp))
         {
             byte[] hashmessage = hmacsha512.ComputeHash(encoding.GetBytes(callParams[1] + ":" + code+ ":" + time));
             headers["Life"] = "" + ByteToString(hashmessage).ToLower();
             headers["Code"] = "" + code;
             headers["Content-type"] = "application/x-www-form-urlencoded";
 
         }
 
         byte[] rawData = form.data;
       
         WWW www = new WWW("https:/www.gameTest/api/", rawData, headers); 
 
         return www; 
     }

The log shows the crash in diferent points. Sometimes here:

 **WWW www2 = OrganizeData(callParams);**

And sometimes in other points:

 **byte[] rawData = form.data;**

And here:

 **WWW www = new WWW("https:/www.gameTest/api/", rawData, headers);** 

In Unity 4 it did not happens. When the project was updated to 5, it happens always... sometimes after 30 minutes, sometimes after some hours.

Someone faced something like this?

Thanks in advance.