ggplot2: recommended workaround for broken legend.position="top"

Searching the mail archives I found that using legend.position as in
p.ring.3 + opts(legend.position="top")

is a known bug. ?I tried doing
p.ring.3 + opts(legend.position=c(0.8, 0.2))

which works, but the legend background is transparent, i.e. I see the
plot background through the legend. ?Adding additional option

opts(legend.background=theme_rect(fill=TRUE,colour="white"))

fills the whole rectangle black(!), making text invisible, but leaves the shape
symbols visible.

So, how can I obtain a graph with legend positioned within the plot boundaries
(that's OK, I don't even mind manually positioning the legend), but on a white
background, i.e., so that the plot underneath is not visible?