ERROR: could not open file "base/.../...": Interrupted system call

After trying to run PostgreSQL 9.1 on Amazon Web Services this error has been turning up in the database and application logs. Reinstalling on a different AWS VM has not helped. Strangely the error goes a way after a few moments of activity, only to return once the system goes idle for a while.

The PostgreSQL data populating the database was recently WAL streamed from a CentOS VM and restarted as a read-write master.

Searches for "EINTR" in the PostgreSQL source turns up plenty of results, but none that jumps out as related to opening base files. Quite a few references to "could not open file". These looked promising:

src/backend/storage/file/copydir.c
src/backend/storage/file/fd.c 
src/port/open.c