Unfortunately, in certain conditions, apt-get will break functionality, and brick your drive. This page has more information. Also see the first step of my OwnCloud install guide.
nfodiz has a great article on unbricking the MBL (I have had to use it on occasion). That’s going to be your best bet.
After that, he also has an article on assigning the reset button to do a recovery.
Best of luck to you!
EDIT: You may also be able to remove the links and re-install at. It could work, since you still have ssh. Worst case: it doesn’t work.
rm -f /var/lib/dpkg/info/wd-nas.*apt-get update
apt-get install --reinstall -y at
EDIT2: You may also want to edit your repository list, as discussed in the OwnCloud setup guide. Edit /etc/apt/sources.list
nano /etc/apt/sources.list
Comment out the indicated lines:
deb http://ftp.us.debian.org/debian/ squeeze main
deb-src http://ftp.us.debian.org/debian/ squeeze main
#deb http://ftp.us.debian.org/debian/ wheezy main
#deb-src http://ftp.us.debian.org/debian/ wheezy main
#deb http://ftp.us.debian.org/debian/ sid main
And try again:
apt-get update
apt-get install --reinstall -y at
