install base system failed : Ubuntu server and xubuntu alternate installation

view full story

http://askubuntu.com – I tried installing Ubuntu 12.04 server on my laptop using a USB stick !! When it reached the base system installation I received this error ! Debootstrap warning warning: file:///cdrom/portal/main/t/tzdata/tzdata_2012b-1_all.deb was corrupt then it sends me back to the menu where I can choose either to install the base system again or proceed without installing it. The same thing happened when I tried to install Xubntu 12.04 alternate on the laptop. Although I can install the Xubuntu using the Normal iso (GUI installation) with no problems ! I used md5su (HowTos)