Which Nike Vapor shoe had the popped air unit problem? Was it the Vapor Speed or the Vapor III's? Also, was there a Vapor II or is that the same as the Vapor Speed? If so, what was the original or first Vapor shoe called? I just got some Vapor III's and am a bit concerned about the air unit eventually popping on them. Anyone else had a problem with the air unit popping on the Vapor III's? Thanks.