hi all, i have been using backtrack 4 for a while now but all of a sudden Synaptics and all Apt-get fail with an error code stating that

reading state infomation ...error
and E: read error - read (5 input/output error)

it works when booting from my pen stick just not the harddrive install, i have tried copying the APT folder from the pen drive to the harddrive but still no good. has anybody had this before? if so how can it be fixed>

thanks in advance