For info, I tried with R 2.14.2 on my cluster, but I get the same errors. So I guess there is some problem with the interaction effect (my cluster, doParallel). 

Rich, do all my package versions match yours?

> require(parallel)
Loading required package: parallel
> cl <- makePSOCKcluster(c("sim18.sugi-lab","sim19.sugi-lab"),
+                        user="hocking",
+                        rscript="/home/hocking/lib64/R/bin/Rscript",
+                        homogeneous=FALSE,
+                        master="192.168.224.47")
> hostname <- function(...)system("hostname",intern=TRUE)
> clusterCall(cl,hostname) #works
[[1]]
[1] "sim18"

[[2]]
[1] "sim19"

> clusterApply(cl,1:2,hostname) #works
[[1]]
[1] "sim18"

[[2]]
[1] "sim19"

> showConnections()
  description           class      mode  text     isopen   can read can write
3 "<-sim18.local:10187" "sockconn" "a+b" "binary" "opened" "yes"    "yes"    
4 "<-sim19.local:10187" "sockconn" "a+b" "binary" "opened" "yes"    "yes"    
> require(doParallel)
Loading required package: doParallel
Loading required package: foreach
foreach: simple, scalable parallel programming from Revolution Analytics
Use Revolution R for scalability, fault tolerance and more.
http://www.revolutionanalytics.com
Loading required package: iterators
> registerDoParallel(cl)
> foreach(i=1:2)%dopar%{
+   hostname()
+ }
Error in unserialize(node$con) : error reading from connection
> clusterCall(cl,hostname) #doesn't work
Error in serialize(data, node$con) : ignoring SIGPIPE signal
> clusterCall(cl,hostname) #doesn't work
Error in serialize(data, node$con) : error writing to connection
> clusterCall(cl,hostname) #doesn't work
Error in serialize(data, node$con) : error writing to connection
> showConnections()
  description           class      mode  text     isopen   can read can write
3 "<-sim18.local:10187" "sockconn" "a+b" "binary" "opened" "yes"    "yes"    
4 "<-sim19.local:10187" "sockconn" "a+b" "binary" "opened" "yes"    "yes"    
> cl <- makePSOCKcluster(rep("localhost",2))
> clusterCall(cl,hostname) #works
[[1]]
[1] "toby-CF-SX2MEKBP"

[[2]]
[1] "toby-CF-SX2MEKBP"

> clusterApply(cl,1:2,hostname) #works
[[1]]
[1] "toby-CF-SX2MEKBP"

[[2]]
[1] "toby-CF-SX2MEKBP"

> registerDoParallel(cl)
> foreach(i=1:2)%dopar%{
+   hostname()
+ } #works
[[1]]
[1] "toby-CF-SX2MEKBP"

[[2]]
[1] "toby-CF-SX2MEKBP"

> clusterCall(cl,hostname) #works
[[1]]
[1] "toby-CF-SX2MEKBP"

[[2]]
[1] "toby-CF-SX2MEKBP"

> showConnections()
  description           class      mode  text     isopen   can read can write
3 "<-sim18.local:10187" "sockconn" "a+b" "binary" "opened" "yes"    "yes"    
4 "<-sim19.local:10187" "sockconn" "a+b" "binary" "opened" "yes"    "yes"    
5 "<-localhost:10187"   "sockconn" "a+b" "binary" "opened" "yes"    "yes"    
6 "<-localhost:10187"   "sockconn" "a+b" "binary" "opened" "yes"    "yes"    
> sessionInfo()
R version 2.14.2 (2012-02-29)
Platform: x86_64-unknown-linux-gnu (64-bit)

locale:
 [1] LC_CTYPE=en_US.UTF-8       LC_NUMERIC=C              
 [3] LC_TIME=en_US.UTF-8        LC_COLLATE=en_US.UTF-8    
 [5] LC_MONETARY=en_US.UTF-8    LC_MESSAGES=en_US.UTF-8   
 [7] LC_PAPER=C                 LC_NAME=C                 
 [9] LC_ADDRESS=C               LC_TELEPHONE=C            
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C       

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

other attached packages:
[1] doParallel_1.0.1   iterators_1.0.6    foreach_1.4.0      ggplot2_0.9.3     
[5] RColorBrewer_1.0-5 lattice_0.20-0    

loaded via a namespace (and not attached):
 [1] codetools_0.2-8  colorspace_1.2-0 compiler_2.14.2  dichromat_1.2-4 
 [5] digest_0.6.0     grid_2.14.2      gtable_0.1.2     labeling_0.1    
 [9] MASS_7.3-17      munsell_0.4      plyr_1.8         proto_0.3-10    
[13] reshape2_1.2.2   scales_0.2.3     stringr_0.6.2   
>
	[[alternative HTML version deleted]]