Problem with NotifyIcon.ShowBalloonTip

Basically the problem is that the following line of code works perfectly on one computer and doesn't appear to do anything on the other (_Icon is a NotifyIcon object). this._Icon.ShowBalloonTip(int.MaxValue, "title", "some text", ToolTipIcon.Info); The computer it works on is running xp professional and the one it doesn't work on is running xp home, but I don't think this should make any difference. Any ideas?