The maximum possible rank number scheduled in Cairo for May is AF42488 (
http://egypt.usembassy.gov/consular/iv8.html ) while cutoff for May is 50,000 for Africa. It is definitely much lower than cutoff.
The number of interview scheduled in Cairo also decreased in May (22 interviwes) versus April (64 interviews)
I suspect that the visa numbers exhausted for Africa. I think there is going to be a second batch of African winners in DV-2012. I suspect the maxumum possible number ever shown to winners is not more than AF43000. The problem is I see some people on the forum from Africa for DV-2012 rank number higher than 43000, even higher that 51000. I saw someone with rank number around AF75000. That contradicts my suspicion. Or it is just an exagerration and the real numbers are lower.
I want you guys with rank number higher than 43,000 to double check you are in fact higher and I want you to tell me if your interview has already been scheduled.