Placing single blocks often lead to block placing spasms that don't stop until pressing esc.

frequently when placing a single block in survival or creative, Minecraft ends up in block placing spasms that continue until esc. is pressed. It's behaving almost as if right click is being held down when nothing is being touched. Happens 100% of the time I drink a potion in creative: I never stop drinking that potion until esc is pressed. Makes minecraft difficult to play on Macs, especially in creative mode. This has been tested on multiple iMacs running 10.5, and the same thing happens.