apt problem: `Packages file <foo> has changed'

[Robin Stephenson <robin.stephenson@blackwell.co.uk>]

I tried to get xv installed last night `apt-get install xv', and got
the following error message:

E: Packages file <foo> has changed.

I had a look on the net, and found a couple of ancient messages
referring to this problem with `deity': the recommendation was to
delete /var/cache/apt/*.bin and update again.

So I did `rm delete /var/cache/apt/*.bin; apt-get update', and now I
get a different error when I try `apt-get install xv':

E: Can't open /var/cache/apr/srcpkgcache.bin

`apt-get update' doesn't seem to have any problems, but `apt-get
install' still doesn't work.  Help!

-- 
 Robin Stephenson
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