[ubuntu-za] Hash Sum Mismatched

[Arnold Pietersen]

Hi

I am upgrading from Karmic to Lucid.  I downloaded the alternate iso.  
At one point I get the following message:

Failed to fetch cdrom:[Ubuntu 10.04 LTS _Lucid Lynx_ - Release i386 
(20100427.1)]/pool/main/f/firefox/firefox_3.6.3+nobinonly-0ubuntu4_i386.deb 
Hash Sum mismatch

Any ideas how I can fix it since I can't move past this point.  I tried 
to google it with no success.

Thanks

ARNOLD