unable to install packages on R-2.13

Dear list,

There seems to be something wrong with my installation of R on a
MacBook Pro running Mac OS 10.5.8. I've tried installing R-2.13 from
r.research.att.com, but install.packages() fails to open the window to
select a mirror,

install.packages("ggplot2")
--- Please select a CRAN mirror for use in this session ---
Loading Tcl/Tk interface ... Error: .onLoad failed in loadNamespace()
for 'tcltk', details:
call: dyn.load(file, DLLpath = DLLpath, ...)
error: unable to load shared object
'/Library/Frameworks/R.framework/Versions/2.13/Resources/library/tcltk/libs/i386/tcltk.so':
dlopen(/Library/Frameworks/R.framework/Versions/2.13/Resources/library/tcltk/libs/i386/tcltk.so,
10): Library not loaded: /usr/local/lib/libtcl8.5.dylib
Referenced from:
/Library/Frameworks/R.framework/Versions/2.13/Resources/library/tcltk/libs/i386/tcltk.so
Reason: image not found

sessionInfo()

R version 2.13.0 alpha (2011-03-23 r54969)
Platform: i386-apple-darwin9.8.0/i386 (32-bit)

locale:
[1] en_GB.UTF-8/en_GB.UTF-8/C/C/en_GB.UTF-8/en_GB.UTF-8

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

For some apparently unrelated reason my attempt at building R from svn
also results in errors when trying to install packages,

[...]
ld warning: in /Library/Frameworks/R.framework/R, file is not of
required architecture
installing to /Library/Frameworks/R.framework/Versions/2.13/Resources/library/plyr/libs/x86_64
** R
** data
**  moving datasets to lazyload DB
** inst
** preparing package for lazy loading
** help
*** installing help indices
** building package indices ...
** testing if installed package can be loaded
Error in library.dynam(lib, package, package.lib) :
shared object 'plyr' not found
Error: loading failed
Execution halted
ERROR: loading failed
* removing ?/Library/Frameworks/R.framework/Versions/2.13/Resources/library/plyr?

I did not explicitely ask for R to use this 64 architecture, as far as
I know (I only typed ./configure ; make ; sudo make install). R-2.14
built from svn works fine, but I'd rather be testing the alpha
release.

What's my best option to get R alpha running? Also, I assume removing
/Library/Frameworks/R.framework/Versions/2.13 altogether is sufficient
to avoid any possibility of interaction between successive
installations, is this correct?

Best regards,

baptiste