It seems that this error is related to your partition.
Boot the aptosid cd and execute the following command as root:
fsck -f -c -p [your partition]
Maybe fsck is able to fix this problem.
If not, you probably have a bigger problem, because some very important files are affected by this Input/Output Error (means that you can't read nor write/delete this file).
In case of critical I/O Errors I migrate my data (/home) to another partition and reinstall the system.
But I don't know how the experts in this forum would react.
EDIT: This threat should be moved to "Installation"
I'm running fsck -f -c -p /dev/sda5 now, seems to be taking a very long time, > 30 minutes so far. 50GB partition.