[R] how to deal with errors

[Thomas Keller]

Greetings,
Could someone give me some help on how to solve problems with  
packages? This worked just yesterday. Today I get an error. ?
 > library(Rcmdr)
Error in structure(.External("dotTclObjv", objv, PACKAGE = "tcltk"),  
class = "tclObj") :
   [tcl] invalid command name "font".

Error : .onAttach failed in 'attachNamespace'
Error: package/namespace load failed for 'Rcmdr'

Here's my system:
 > str(.Platform)
List of 8
  $ OS.type   : chr "unix" ## OS X 10.5.6, R version 2.8.1
  $ file.sep  : chr "/"
  $ dynlib.ext: chr ".so"
  $ GUI       : chr "AQUA"
  $ endian    : chr "little"
  $ pkgType   : chr "mac.binary"
  $ path.sep  : chr ":"
  $ r_arch    : chr "i386"