[R-SIG-Mac] /bin/sh: tar: command not found

[Andrew Noble]

Today, I downloaded the most recent binary for R.app.  I'm running on 
MacOSX 10.4.11.

Downloading packages fail.  I've tried it at the command line and 
using the "Packages & Data" menu.  In both cases, trying to 
downloaded the "emdbook" binary, I get the following error.

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Warning in install.packages("emdbook") :
   argument 'lib' is missing: using '/Users/andrewnoble/Library/R/2.7/library'
trying URL 
'http://cran.mirrors.hoobly.com/bin/macosx/universal/contrib/2.7/emdbook_1.1.1.tgz'
Content type 'application/x-tgz' length 126320 bytes (123 Kb)
opened URL
==================================================
downloaded 123 Kb

/bin/sh: line 1: tar: command not found
Error in sprintf(gettext(fmt, domain = domain), ...) :
   argument is missing, with no default---
-----

Any help would be greatly appreciated.  Thank you!
Andrew