Linksys Extender Aspect Ratio problem

I have a home built media center PC which works great using a Hauppauge 150
card. Live and recorded TV (4:3 ratio) work fine locally on the MCE PC, but
when I use a Linksys extender both live and recorded TV and My Pictures get
squashed horizontally to something like a 3:3 format (no loss, just squashed)
with a black band on the left and right of the image. The main extender menus
are fine and the TV preview appears in the very bottom left corner as it
should on the main menu, but when I go to sub-menus (such as when I select My
TV) the preview moves to the right a couple of inches as if the sub-menus are
also being squashed to a 3:3 format, however the background image is
unaffected and fills the screen. I have tried different video outputs on the
extender and a couple of TVs with the same results. If I plug the same TVs
directly in to the Media Center PC the ratio is fine. Recorded Program also
play OK on other systems - Media Player 10 and Vista Media Center.

I have all rollups, etc pushed from Window Update applied to the MCE PC and
Rollup 1 for LinkSys applied to the Extender.

Linksys support has been useless (they seem to have no clue about the
extender). Any assistance appreciated. Many thanks