I'm an mbox user, where my inbox is a file like /var/spool/mail/don. After this morning's security announcement I upgraded from pine 4.44-r4 to 4.50-r1. However after that my inbox didn't have my mail. My saved message folders were there and read fine. I looked in /var/spool/mail/don and all the new mail was still there and piling up. So I commented the maildir support patch and re-emerged and it works now, after warning me that /var/spool/mail needed to be chmod 1777. FYI.
pine-4.50-r3 has been released into portage. The ebuild now properly supports the mbox USE variable.