From: "Björn Latte" <bl@...>

One of the most common causes of checksum errors that I've encountered is
anti-virus software that doesn't have the database directories excluded.
This may or may not be a problem for you but so far, it 's the only problem
I've ever found when this occured and it always cured the problem when it
was corrected.

HTH
Woody (TMW)