R hangs in nls "port" routine

You should also report R.Version() and sessionInfo() and also if  
you are using CRAn version of R or your own build. Sometimes is it  
of help.

Many apologies. I realised that I had forgotten to do this. The build  
is the standard binary build from CRAN. Relevant outputs below

 > R.Version()
$platform
[1] "i386-apple-darwin8.8.1"

$arch
[1] "i386"

$os
[1] "darwin8.8.1"

$system
[1] "i386, darwin8.8.1"

$status
[1] ""

$major
[1] "2"

$minor
[1] "4.0"

$year
[1] "2006"

$month
[1] "10"

$day
[1] "03"

$`svn rev`
[1] "39566"

$language
[1] "R"

$version.string
[1] "R version 2.4.0 (2006-10-03)"

 > sessionInfo()
R version 2.4.0 (2006-10-03)
i386-apple-darwin8.8.1

locale:
C

attached base packages:
[1] "grid"      "methods"   "stats"     "graphics"  "grDevices" "utils"
[7] "datasets"  "base"

other attached packages:
       rgl   lattice   spatial
    "0.68" "0.14-13"  "7.2-29"
 >