problem with opening more than one SOCK cluster with package snow

Dear list,

i have some problems using the snow package to create a SOCK cluster.
The errors just occour irregularly but it seems to me that they occour
when I try to create more than one cluster on the same machine via
different R instances started via submitting LSF jobs to a cluster. Does
anyone have an idea how to solve this or where to start digging for
solutions?

The error messages are:

library(snow)
cl <- makeCluster(8, type = "SOCK")


Error in socketConnection(port = port, server = TRUE, blocking = TRUE,  :
   cannot open the connection
Calls: run.call ... makeCluster -> makeSOCKcluster -> newSOCKnode ->
socketConnection
In addition: Warning message:
In socketConnection(port = port, server = TRUE, blocking = TRUE,  :
   port 10187 cannot be opened


R version 2.15.1 (2012-06-22)
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] stats     graphics  grDevices datasets  utils     methods   base

other attached packages:
[1] snow_0.3-10


Thanks a lot
Jannis