apt-get upgrade error

[Paul Cartwright <debian@pcartwright.com>]

ever since my upgrade to squeeze I am getting errors like this ( more of 
them):

warning, in file '/var/lib/dpkg/available' near line 514018 package 
'virtualbox-2.2':
 error in Version string '2.2.4-47978_Debian_lenny': invalid character 
in revision number
warning, in file '/var/lib/dpkg/available' near line 514157 package 
'virtualbox-2.0':
 error in Version string '2.0.6-39765_Debian_lenny': invalid character 
in revision number
warning, in file '/var/lib/dpkg/available' near line 514268 package 
'virtualbox-2.1':
 error in Version string '2.1.4-42893_Debian_lenny': invalid character 
in revision number
Processing triggers for python-central ...

virtualbox has been purged from my system, but that file:
# ls -l /var/lib/dpkg/available
-rw-r--r-- 1 root root 25094284 Feb 19 08:00 /var/lib/dpkg/available

is rather large...

--
Paul Cartwright