I had a similar experience when I was doing The Master Cleanse with a parasite cleanse. On day nine I was at a large craft fair with a friend when I started blacking out. I actually had to plop down on the cold wet ground to keep from passing out. My friend insisted I needed to eat (I just told her I didn't have breakfast, not that I was doing a cleanse). Since she doesn't drive I had to proceed to the nearest city about 15 miles away in search of a place where we could eat. The first place was a McDonald's, I had a salad while she had a burger and fries. I was revived enough to feel much better and feel confident about driving. I also decided it was time to break the fast.
When such episodes happen it can be from a massive cleansing crisis where the body is simply too toxic to function. When that happens the only thing to do is to break the fast or go to bed and stay there. That is why water only fasters are urged to get near complete bedrest. Water Fasting usually results in releasing about three times as many toxins into the blood stream than Master Cleanse or sweet juice fasting. Green juice fasting causes a greater release of toxins because there is less Sugar to metabolize.
Other reasons for blackouts when fasting is a sudden drop in blood pressure or an electrolyte imbalance. Both of these problems need to be addressed;however, electrolyte imbalances are unlikely with The Master Cleanse unless too much water is ingested causing an electrolyte flush through the kidneys. If you were losing a lot of fluid from the salt water flush, an electrolyte imbalance is a greater possibility. In some people (like me)the salt water flush can cause a dangerous spike in blood pressure, but the dizziness is a profound sinking type that pretty well immobilizes you.
Whatever caused your blackouts and dizziness, I think you were wise to stop the cleanse. While cleansing crisis and detox symptoms can be expected, that should not be allowed to render you non-functional; and of course, no cleanse is worth risking your life or the lives of your family. Concentrate on rebuilding for a while, The Master Cleanse will be there when you are ready to try again.