[luatex] latest round of updates to fontspec and related packages seems to disable ligatures in Opentype fonts

[Mico Loretan]

Greetings!

I'm running MacTeX2013 pre-release, on a system running MacOSX 10.7.5. I've installed all the latest packages via tlmgr through this morning. The header line from the .log file says:

     This is LuaTeX, Version beta-0.76.0-2013051018 (rev 4627)  (format=lualatex 2013.5.12)  

Consider the following MWE; Garamond Premier Pro is a system font distributed with Macs:

  \documentclass{article}
  \usepackage{fontspec}
  \setmainfont[Ligatures={Common,Rare}]{Garamond Premier Pro}
  \begin{document}
  off fit fly office baffle 

  act stab spoon 
  \end{document}

Since running the latest round of updates on all packages, neither the "common" ligatures (see the words in the first line after \begin{document} nor the "rare" ligatures (the following line) are being produced any longer. This problem also occurs if I use the font "Sabon Next LT Pro Regular". 

In contrast, if I use the font "EB Garamond" (a "free" opentype font(), the common ligatures are generated but *not* the rare ones. Finally, if I use "Latin Modern Roman", the common ligatures are also produced correctly; of course, Latin Modern doesn't feature "rare" ligatures, so I can't tell if the problem with rare ligatures not being produced extends to Latin Modern Roman...

I've never experienced a problem like this before. Are there some font cache file I need to wipe out and rebuild, or is the problem seated at some deeper, darker level?