It looks like your clock was at some point very wrong:
0~$ ls -lh /var/lib/apt/periodic/ insgesamt 0 -rw-r--r-- 1 root root 0 2012-06-11 06:56 update-stamp
If you delete this file, it should work again.
It looks like your clock was at some point very wrong:
0~$ ls -lh /var/lib/ apt/periodic/
insgesamt 0
-rw-r--r-- 1 root root 0 2012-06-11 06:56 update-stamp
If you delete this file, it should work again.