I found the answer to this: the partition had filled up, and so the problem

was lack of disk space.

Oliver Elphick

src/backend/access/transam/xlog.c

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Header: /cvsroot/pgsql/src/backend/access/transam/xlog.c,v 1.65 2001/04/05 16:55:21 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/access/transam/xlog.c,v 1.66 2001/05/22 16:52:49 momjian Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -1334,7 +1334,7 @@ XLogFileInit(uint32 log, uint32 seg,
 			unlink(tmppath);
 			errno = save_errno;
 
-			elog(STOP, "ZeroFill(%s) failed: %m", tmppath);
+			elog(STOP, "ZeroFill failed to create or write %s: %m", tmppath);
 		}
 	}