did you prep for this at all with diet restriction prior to going on the cleanse?
no caffine, no processed foods, etc?
headaches are a detox symptom. if you would of just had another lemonade and drank alot more water it would of gotten better.

try it.
i get migranes too. now instead of taking a pill i just drink alot of clean water and try to rest. its not gone in 15 minutes but i am not putting chemicals in my body that are so great for it.
also i noticed doing it this way (drinking water and resting) they are less frequent and less painful

The Master-Cleanse is a great way to find out what is triggering your migranes. They have to be happening for a reason right? The first Master-Cleanse I did I made sure to ween myself off coffee a week before I did it. Even still, I manged to get a migrane on day 3 that lasted 2 days. I get migranes regularly so I wasn't that surpised.. but it was none too pleasant. I manged to stay on the cleanse by taking a lot of hot baths in the dark and resting in a cool room with an ice pack on my face.

since my first cleanse I haven't had a migrane. I just finshed my second cleanse and the only time I got a migrane was the night I spent in a smoke filled loud bar - I was standing next to the speaker. so it was my own damn fault. :)

Sounds like yours was a sign of detox and is fairly normal. If you still want to, I'd highly suggest going though and trying the cleanse again, migranes and all. I'm glad I did, like I said, I haven't had one since my first cleanse. :)