Freeweight Death Grip

I'm slowly working my way through Strong and did day 23 upper body descending rep workout today. Love this one, but for some reason, right from the start I had total death grip! Holding on the the weights way too hard. Putting them down and shaking out my hands didn't help. Finally I even took off and put back on my gloves (I have baby hands that complain even about the padded handles of the Power Blocks), but that didn't help either. I made it through the workout but my hands are even more tired than the rest of my upper body (which is actually just jell-o right now). This happens rarely but I can't figure out why and my brains don't seem strong enough to override the death grip. Anyone else ever have this problem?