Try installing it again, maybe your repository was updating and the version your Pi was looking for had been superceded. And sync and reboot first, Pi's can get confused and give strange error messages, especially if your file system has gotten corrupted by, for example, turning it off without officially shutting down with a poweroff command. Run a fsck.ext4 to make sure it is intact, if you can put your SD card on another Linux box.
FORUM TIP: To view just one person's posting history, sign in, click on their user name, then click on "Search User's Posts." || My 512MB Model B only runs Arch.