xfce doesn't recognize screen height on rotation

[Micha Feigin <michf@post.tau.ac.il>]

I'm trying to get xrandr -o left to work properly with an nvidia card on two
machines under xfce (rotate the screen). The problem seems to be that the
screen rotates but either X or xfce doesn't realize the change and when I
maximize windows the maximize horizontally but vertically they only go to the
previous resolution (about 3/4 of the screen)

Any ideas?
Thanks