What happened to my 24-70mm 2.8?

I was in the western Caribbean last week on a cruise when on a 87* day my lens zoom ring suddenly froze up on the 50mm mark. I had to force it to go beyond 50mm to 70mm. At the same time the zoom rubber grip became very sloppy and was strectching out of shape. I was quite worried at the time but when I got back to Tampa, FL the rubber grip was tight again and the zooming problem went away completely. What the hell gives????? Anyone ever have a problem like this? I could understand the rubber grip part due to heat but not the zoom sticking. Any solution short of sending it back to Nikon?

Dennis