problems with mp_projections

[a.larkin@xxxxxxxx]

Hello, I am using the mp_projection scripts to make nice polar plots, and
after using go mp_stereographic_north successfully I began to use the 
mp_stereographic_south. I thought that all I'd have to change would be the 
region from y=10:90 to y=-10:-90. But although my routine begins to produce
the plot, during ppl fill it fails with the message
**ERROR: illegal limits: "MASKED_X_PAGE" is not in the range Y=-90:-10
Axis extremes are Y=0.5;10000000
plot/set/vs/nolab/line=1/i=1:22585/overlay masked_x_page, masked_y_page
Command file, command group, or REPEAT execution aborted.
my script is as follows...

set viewport 1
set region/x=0:360/y=-10:-90/z=500
set grid t_ave
go mp_stereographic_south
go margins 0.8,2.8,0.2,0.8
fill/noaxis/levels=(-0.6,1.3,0.1)/set_up diff[z=500,l=1:12@ave], x_page, y_page
ppl labs 4,0,0@as;ppl labs 5,0,0@as;ppl title "500 mbar"
go remove_logo
ppl fill
go mp_land
go mp_graticule 0 360 30 -10 -90 15
Please help 
Thanks
Alice