Can't set background color in 4.2.5 on jpeg terminal

The following script produces a plot with a black background and a red trace on gnuplot 4.0.0, but produces a plot with a white background and red trace on gnuplot 4.5.2.

One from a fresh install on OSX 10.5.7 via Fink. The other from a fresh install via Macports. (As in both Fink and Macports were completely removed and both port systems reinstalled from scratch.)

Is this a known bug or a known library configuration issue?

Thanks.

- Rod

gnuplot > file.jpg  <<XXX
set term jpeg size 1200,90 x000000 xffffff x0000ff xff0000
set datafile separator ","
plot [0.01: 3] 'file.csv' using 1:2 notitle  with lines
XXX