as far as firefox goes...if you're using firefox 1.5, i noticed i had to go into firefox and change display resolutions to "system settings"
you can get there from firefox edit>preferences>content and choose the advanced button under fonts & colors...and switch the display resolution there. i forget what mine was set at originally, but it seems i had the same problem you do...
once i set it to "system settings" my fonts fell right into place nicely
