Intermittent connectivity issues for JDBC / Oracle

I have been experiencing issues with an R script hanging when connecting to
an Oracle database.  To help debug, I found a function here in the nabble
forum and made a small test script:

  #!/usr/bin/Rscript --no-restore --no-save --no-init-file
  library("RJDBC")
  drv<-JDBC("oracle.jdbc.OracleDriver","/home/oracle/lib/ojdbc6.jar", "'")

  dbCheck = function(url, user='', pwd='') {
    j = .jcall("java/sql/DriverManager", "Ljava/sql/Connection;",
  "getConnection", url, user, pwd, check=FALSE)
    x = .jgetEx()
    .jcheck()
    x
  }
  dbCheck("jdbc:oracle:thin:@192.168.3.10:1521:psrndpt1","myuser","mypass")


When I run the file - sometimes it works, returning NULL, and sometimes it
hangs for between 1 and 2.5 minutes before throwing an error.  The database
is new and stable, on the same network - with no connection issues from any
other clients.  This machine isn't currently doing anything else except for
running this script.  Output from running it several times looks like this:

R at ss-dev:~/scripts$ ./dbCheck.R
Loading required package: methods
Loading required package: DBI
Loading required package: rJava
NULL
R at ss-dev:~/scripts$ ./dbCheck.R
Loading required package: methods
Loading required package: DBI
Loading required package: rJava
NULL
R at ss-dev:~/scripts$ ./dbCheck.R
Loading required package: methods
Loading required package: DBI
Loading required package: rJava
NULL
R at ss-dev:~/scripts$ ./dbCheck.R
Loading required package: methods
Loading required package: DBI
Loading required package: rJava
NULL
R at ss-dev:~/scripts$ ./dbCheck.R
Loading required package: methods
Loading required package: DBI
Loading required package: rJava
NULL
R at ss-dev:~/scripts$ ./dbCheck.R
Loading required package: methods
Loading required package: DBI
Loading required package: rJava
NULL
R at ss-dev:~/scripts$ ./dbCheck.R
Loading required package: methods
Loading required package: DBI
Loading required package: rJava
Error in .jcall("java/sql/DriverManager", "Ljava/sql/Connection;",
"getConnection",  :
  ignoring SIGPIPE signal
Calls: dbCheck -> .jcall -> .External
Execution halted
R at ss-dev:~/scripts$ ./dbCheck.R
Loading required package: methods
Loading required package: DBI
Loading required package: rJava
Error in .jcall("java/sql/DriverManager", "Ljava/sql/Connection;",
"getConnection",  :
  ignoring SIGPIPE signal
Calls: dbCheck -> .jcall -> .External
Execution halted
R at ss-dev:~/scripts$ ./dbCheck.R
Loading required package: methods
Loading required package: DBI
Loading required package: rJava
NULL
R at ss-dev:~/scripts$ ./dbCheck.R
Loading required package: methods
Loading required package: DBI
Loading required package: rJava
Error in .jcall("java/sql/DriverManager", "Ljava/sql/Connection;",
"getConnection",  :
  ignoring SIGPIPE signal
Calls: dbCheck -> .jcall -> .External
Execution halted


The times that it returns NULL, it returns immediately.  When it throws the
error, it is a varying amount of time between roughly 1 and 2.5 minutes.
Both machines are not busy at all.

Any ideas would greatly appreciated.  Thanks.