dpkg seems not to 'see' virtual package installed.

[Prekates Alexandros <aprekates@gmail.com>]

i experience a problem in ubuntu 10.04 of not being able to install a third-party deb package with dpkg. And if i install it with ignore flags afterwards apt wont leave me install anything unless i remove the third party package . Sorry if not related. I'm a user of dpkg and it seems to me that maybe the bevahior i see has sth to do either with a maloformed third party package either with a dpkg strange behavior, and as i see in that bug report is still unsolved (https://bugs.launchpad.net/ubuntu/+bug/480903)

Analytically my problem:

In my Lucid 10.04 trying to make my canon pixma 3600 work i downloaded from canon the driver which is the file:
ip3600_debian_printer.tar

and it contains two deb packages:
cnijfilter-common
cnijfilter-ip3600series
and cnijfilter-common-3.00-1.tar.gz

For cnijfilter-common holds:
Depends: libc6 (>= 2.3.4-1), libcup
sys2 (>= 1.2.1), libpopt0 (>= 1.7)

And for the installed libcups2 in lucid 10.04 holds:
Replaces: libcupsys2 (<< 1.3.7-6)
Provides: libcupsys2
Conflicts: libcupsys2 (<< 1.3.7-6)

but:
sudo dpkg -i cnijfilter-common_3.00-1_i386.deb (translating some errors from greek)
Decompressing cnijfilter-common (από cnijfilter-common_3.00-1_i386.deb) ...
dpkg: dependencies problems prevent configuration of cnijfilter-common:
cnijfilter-common depends from libcupsys2 (>= 1.2.1). But:
Package libcupsys2 in not installed

Why is the last true since the virtual package libcupsys2 is installed?

thanks

alex prekates