problem with postscript command

please, when i use the command postscript, the symbol "<="(less than or
   equal to) is replaced by "..." (ellipsis)
   how can I fix that?
   postscript("plot1.ps", width = 22, height =
   11.5,pointsize=24,paper="special",bg="transparent")
   plot(NULL,xlim=c(1,10),ylim=c(1,10))
   text(5,5,"\u2264")
   dev.off()
   I'm using windows vista, my system is in English, R v2.8.1
   thanks, Victor