asterix:~# apt-get install --reinstall ntp
Reading package lists... Done
Building dependency tree... Done
0 upgraded, 0 newly installed, 1 reinstalled, 0 to remove and 7 not upgraded.
Need to get 0B/330kB of archives.
After unpacking 0B of additional disk space will be used.
Do you want to continue [Y/n]? 
E: Invalid archive signature
E: Prior errors apply to /var/cache/apt/archives/ntp_1%3a4.2.2.p4+dfsg-2_i386.deb
debconf: apt-extracttemplates failed: Bad file descriptordpkg-deb: `/var/cache/apt/archives/ntp_1%3a4.2.2.p4+dfsg-2_i386.deb' is not a debian format archive
dpkg: error processing /var/cache/apt/archives/ntp_1%3a4.2.2.p4+dfsg-2_i386.deb (--unpack):
 subprocess dpkg-deb --control returned error exit status 2
Errors were encountered while processing:
 /var/cache/apt/archives/ntp_1%3a4.2.2.p4+dfsg-2_i386.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)