Loop not looping ?

This works fine when the IP address is valid, however when it is not, it does loop - I can see it in the system tray  but when I make the IP address live again the MsgBox won't pop up.
Can someone point me in the right direction so it does or let me know what I have done wrong ?

$IP = Ping("10.20.32.166",3000)
While 1
If $IP Then
MsgBox(64,"It's Alive","It's Alive")
Exit
If @error Then ContinueLoop
EndIf
WEnd