Beginning a round I found I had just run out of balls and took the option to purchase a new sleeve. The page went black and froze for a number of minutes with a rotating circle. I restarted the round and chose again to purchase within the game - same result.
After restarting the game, I went to the Pro Shop and purchased a new sleeve successfully.
The next day, I was informed that I had purchased 3 sleeves of balls and was charged 900 credits!
I guess I'm set for balls for awhile, but this has certainly screwed up my budget plans!