format() applied to an NA character string (PR#9616)

I get strange results when I try to format() an NA character string.

x <- 'sometext'
x[1] <- NA
format(NA, width=32) # displays sensibly, right-justified
format(x,width=32)   # displays sensibly, left-justified
format(x,width=33)   # displays ""
format(x,width=36)   # R exits abnormally with code 5

version

platform       i386-pc-mingw32
arch           i386
os             mingw32
system         i386, mingw32
status
major          2
minor          4.1
year           2006
month          12
day            18
svn rev        40228
language       R
version.string R version 2.4.1 (2006-12-18)

I'm running Windows XP.

Damon.