trouble with cloud output to bmp when in loop

I have some data that I need to view in various 3-D clouds.  To better see
the cloud structure on a 2-D screen I would like to output a bunch of bmp
files with clouds at slightly different angles, then run them through an
external program to animate them.  But I'm having trouble getting cloud()
from the lattice package to output to bmp files.  Oddly, this is only a
problem when outputting multiple files in a loop.

WORKS FINE:

 bmp("d:/test2.bmp"); cloud(z~x+y); dev.off()

ALSO WORKS:

bmp("d:/test01.bmp"); cloud(z~x+y); dev.off(); bmp("d:/test02.bmp");

cloud(z~x+y); dev.off();

DOES NOT WORK (produces blank bitmaps):

for(i in 1:3) {bmp("d:/test2.bmp"); cloud(z~x+y); dev.off()}

Is this a bug?