During the last annual on N209RV (RV-9A) I decided that I should grease the prop hub. I've flown at least three times since then with no indication of a problem. Yesterday's flight however was different. The preflight inspection showed no problems. Runup and takeoff was fine but on climb out I started to see the windscreen being covered with something. It was not streking off and in just a minute or two the passenger side was hard to see through. I made a quick 180 and put in a slip to get back on the ground since I didn't know what was going on or how long before the left side was covered too. Back on the ground I removed the spinner and found that one of the grease fittings, a zerk, had failed. Grease had flung out of it. Upon removal it was apparent the check ball was not sealing. I'm assuming that greasing the hub had forced some dirt into it. Now to get that replaced and grease it again. All's well that ends well.