blurry image on Intel graphics through an add-on DVI card

[Lintula]

We are having an unexpected problem with add-on DVI cards to Lenovo M55
model 8808-97G and 8811-92G workstations. While they do work in the
sense of displaying graphics, the result is unsatisfactory due to
looking blurred. In fact the graphics are much sharper when brought
through the integrated VGA connector!

Incorrect resolution is not likely the problem, since all the monitors
report it being what they expect. They also report the signal as
digital, and it can pass through a cable with DVI-D connectors.

At least the 8811 has Intel 965Q graphics. I cannot test 8808 right now,
but it should be substantially similar if not the same. The problem is
visible at least in the brand new Red Hat Enterprise Linux 5, as well as
a less strictly versioned Gentoo installation. Under Windows a similar
setup displays a sharp image.

The cards that are sold for the model are of the type ADD2-R, but I also
tried an ADD2-N card and there was no change in result - both worked but
displayed a blurry image. The only source of blurredness left that I can
think of is an unnecessary D/A->A/D conversion somewhere along the line
due to factors unknown.

I would be grateful for any information or ideas.