Vim compiled with +clipboard, but both + and * registers are unable to store yanks

I am using Vim 7.4 homebrew version on Mavericks, with +clipboard. Under both vim and MacVim, yanking into either + or * has no effect and pasting from either one produces an error E353: Nothing in register * (or +).

Steps to produce it:

1. $ vim -u None
2. Insert some text
3. "*yy
4. "*p => E353: Nothing in register *
5. :echo has("clipboard") => 1

This also means that both set clipboard=unnamed and set clipboard=unnamedplus cannot properly copy & paste. Can anyone suggest how I can troubleshoot this problem?

Thanks!

Related questions:

• How to make vim paste from (and copy to) system's clipboard? The accepted answer suggests:

  try using "*yy or "+yy to copy a line to your system's clipboard. One or the other should work.

  But both registers have no effect.

• https://superuser.com/questions/680609/is-macvim-copy-to-clipboard-supposed-to-be-working-on-os-x-mavericks