see http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=%23626457

AND http://lists.debian.org/debian-devel/2011/05/msg00558.html [working commands]

libc6 2.13-3 may make your system UNBOOTABLE [only on 64-bit]

sposedly fixed in 2.13-4

UPDATE: the 'fixed' libc6 2.13-4 is now hitting the mirrors