Gangplank ultimate failure

I was playing gangplank on ARAM and i died with my ultimate still going and when it came off of cooldown i would no longer activate when i tried to cast it. the targeting part of the ability would activate but i was unable to select an area to target. I have not had an opprotunity to test to see if i could repeat it.

1. pick gangplank on howling abyss
2. get low health
3. cast ultimate 4)have another player kill you right as you cast