This happened to me twice last weekend. Pulled up to the first spot of the day, throwing a spinnerbait. I catch one fish on my second cast then not another bite in several hours. Happened the next day, different spot, same conditions, on a squarebill. Did they go tell their buddies "don't eat that"?

This is on a river that normally is pretty easy to catch fish by fishing the back side of current breaks, but not much water is moving lately. It is basically just a lake right now.

Somewhat like the "first cast curse". 

No current in a body of water that normally has current is a kiss of death. That current oxygenates the water and pushes the fish to current breaks and gets them active. Calm water allows the to roam around a lot more instead of being in the obvious areas. 

Calm water... Could mean you're making too big of a presence and scaring the fish. 

Already been mentioned.  The lack of current is the key.  Without the current the bass are free to roam.  Cover as much water as you can and change your presentations/colors more often.  Worst case go finesse.

Whenever I catch a good fish as my first fish, I might as well pack up and go home because that's it for the day!