After years without problems, suddenly several programs in my installation of cygwin64 on 64-bit Windows 7 Professional are failing to run, and instead appear to exit immediately with code 127, which usually means "command not found" in Bash. In particular, programs like vim, emacs, and even clear exhibit this behavior, while others like vi, echo, touch, and date seem to operate normally.
At first, I figured something might have gone wrong with a previous round of package updates, so I ran another update using cygwin setup's command-line interface, but it didn't seem to help.
From what I can tell, the affected programs don't work at all. Not even --version flags to the program work, which makes me think that there may be something wrong with cygwin itself or a common dependency:
$ vim --version
$ echo $?
127
(I can provide specific version numbers for various packages if it will help, but since this problem existed both before and after the most recent updates, I doubt it matters much.)
I double-checked my PATH variable, and it begins with /usr/local/bin:/usr/bin:, as expected. Is there perhaps some new dependency in these programs that isn't being properly resolved by cygwin's package manager or which may not have been automatically added to my PATH?
Am I missing something else obvious?