can't see css in design mode with visual studio 2008

[graphicsxp@googlemail.com]

Hi,

Since I've migrated my application from 2005 to 2008, I can no longer
see the pages in Design mode. All my pages belong to the same master
page, which has a link to the css file.

I've done a quick test with an empty page, and if I don't use the
styles defined in my css file, I can see the elements in design mode.
However as soon as I apply a style to one of my elements using a class
defined in my css file, the page goes grey in design mode and I can no
longer see the elements.

Is it a known bug, or is there something i'm missing ?

Thanks