title: Parallel processing in caret does not work on R 2.13.0
body: <p>I am using R package <strong>caret</strong> and parallel processing doesn't work. If I try to run example from the <code>train</code> function:</p>
  
  <pre><code>library(mlbench)
  data(BostonHousing)
  
  library(doMC)
  registerDoMC(2)
  
  ## NOTE: don't run models form RWeka when using
  ### multicore. The session will crash.
  
  ## The code for train() does not change:
  set.seed(1)
  usingMC &lt;-  train(medv ~ .,
                    data = BostonHousing, 
                    "glmboost")
  </code></pre>
  
  <p>I get the following error:</p>
  
  <pre><code>Error in names(resamples) &lt;- gsub("^\\.", "", names(resamples)) : 
    attempt to set an attribute on NULL
  </code></pre>
  
  <p>I am using MacBook Pro, early 2011 model with 2.3GHz Intel Core i5 and Mac OS X 10.6.8. </p>
  
  <p>R Session Info:</p>
  
  <blockquote>
    <p>R version 2.13.0 (2011-04-13) Platform:
    x86_64-apple-darwin9.8.0/x86_64 (64-bit)</p>
    
    <p>attached base packages: [1] stats     graphics  grDevices utils<br>
    datasets  methods   base     </p>
    
    <p>other attached packages:  [1] caret_5.13-20   cluster_1.14.2 
    reshape_0.8.4   plyr_1.7.1      lattice_0.19-33 mlbench_2.1-0<br>
    doMC_1.2.3      multicore_0.1-7  [9] foreach_1.3.2   codetools_0.2-8
    iterators_1.0.5</p>
    
    <p>loaded via a namespace (and not attached): [1] compiler_2.13.0
    grid_2.13.0     rpart_3.1-51    tools_2.13.0</p>
  </blockquote>
  
  <p>Is there something I can do to fix this?</p>