Firefox and onblur event

Hello,

I have an ASP.Net application where all my TextBox components contain the "onblur" and "onfocus" events.

The principle:
- I'd like to allow the text selection in the control (when focusing)
- I'd like to disable the text selection of my page when outside the control (on onblur)

So, I have this code on the onfocus event :

Code:

---

function SetBodyDragOn(o)
{
  document.body.onselectstart = new Function("return true;");
  document.body.ondragstart = new Function("return true;");
  document.body.onselect = new Function("return true;");
 
  // Set an edit design class on the textbox control
  if (o)
    o.className = "InputEditingOn";
}

---

And this one on the onblur event :

Code:

---

function SetBodyDragOff(event, o)
{
  if (typeof event.preventDefault != 'undefined') event.preventDefault();
  document.body.onselectstart = new Function(" {event.returnValue=false; try { event.stopPropagation(); event.preventDefault() } catch (ex) {alert(ex.message)} return false; } ");
  document.body.ondragstart = new Function(" {event.returnValue=false; try { event.stopPropagation(); event.preventDefault() } catch (ex) {alert(ex.message)} return false; } ");
  document.body.onselect = new Function(" {event.returnValue=false; try { event.stopPropagation(); event.preventDefault() } catch (ex) {alert(ex.message)} return false; } ");
 
  // Set a standard design class on the textbox control
  if (o)
    o.className = "InputEditingOff";
}

---

With all the browsers (even Firefox), it works fine during one moment.
After a certain time of using, on Firefox, the onblur is not fired.
The cursor stays in the control.

Why this behavior?
Why it works a certain time and not after (memory problem?)
To soluce the problem, I have to reboot my Firefox.

Thanks in advance,
Yannis.