Creaking Windows/ Door Frames (new Focus)

[Beancounter]

Hey all,
I have a 5 door Zetec that is the best car I have ever owned. However everytime that I pull into a drive way or drive over uneven tarmac or take off from a standing start the windows creak. You can mimic the problem by gently pushing on the door glass.
To me (and I am not overly mechanical) it seems that there is chassis flex going on. When the suspension is compressed the chassis is flexing to cause friction between the door seals and hence the creaking/groaning.

I have taken it back to the dealer 4 times in the last 5 months (been doing it since new, Dec 05) and they can't fix it. They have even tried re-aligning my doors and this did nothing. Their final solution was to spray silicon spray the door frame to provide a slick surface. This works for a week or so but it comes back. My concern is that that there is something wrong at a more serious level. I am also annoyed that with a brand new car these sorts of band aid fixes are required.

I am interested to know if anyone with a new Focus (South African built) has experienced creaking windows or door frames also. Is this a fairly unique issue and I am just unlucky or is there a wider issue here.

Thanks in advance

Cheers
Steve
Auckland NZ