Actually, the Five Whys isn't about finding a solution, it is about finding the core problem. I don't think that Joel's example is a good one, because after four true layers of problems it abruptly jumps to a solution, with absolutely no reasoning why this particular solution would be the best one, while leaving deeper issues just to keep the number of Whys at five.
The correct Five Whys process would continue past five questions, and end in something like "because the team is not prepared" or even "the team doesn't have enough experience with organizing events"; something that could be solved by, among others, preparing a checklist.
The correct Five Whys process would continue past five questions, and end in something like "because the team is not prepared" or even "the team doesn't have enough experience with organizing events"; something that could be solved by, among others, preparing a checklist.