I'm wondering whether I get multiple alerts for the same message because sometimes I have more than 1 window going for NGA.
Here's a message I got 3 times but don't remember how many windows I had up for NGA at the time. I don't think it was more than one:
On July 4th I received this message before 1pm, at 2:31pm and 2:34pm. Each time I exited out of the system message only to have the alert icon be lit again and the same message showing up after clicking onto message icon.