I received 1 points for joining and 50 points for registering my email, but I still can't post. 51 points show up in the top bar on the main page, but when I go to post, the top bar says I only have 1 point, and "You must have at least 5 reputation on Area 51 to ask a question."
From the Area 51 FAQ:
You'll earn your first 50 reputation by confirming your email address. This allows you to create proposals and example questions. (Emphasis added)
This is hard to reconcile with the statement:
You must have at least 5 reputation on Area 51 to ask a question. (Emphasis added)
As in the accepted answer below -- it apparently takes time for the reputation to propagate, but wouldn't it be useful in that case to document this fact in the FAQ, so that more people don't end up getting confused like I did?