Oracle RAC intermittent connection

[Dan Parsons]

I am connecting to Oracle 10g RAC using JDBC in Tomcat 6.0.20.
It works around 50% of the time. When it doesnt work it shows this error message:
IO exception: The Network Adapter could not establish the connection.

Here is my JDBC String:

jdbc:oracle:thin:@(DESCRIPTION=(LOAD_BALANCE=on) (ADDRESS=(PROTOCOL=TCP)
(HOST=170.11.5.111) (PORT=1521)) (ADDRESS=(PROTOCOL=TCP)(HOST=170.11.5.112)
(PORT=1521)) (CONNECT_DATA=(SERVICE_NAME=service)   (FAILOVER_MODE =    
(TYPE = SELECT)     (METHOD = BASIC)     (RETRIES = 180)     (DELAY = 5)   )))

The above Description parameters I use in my tnsnames.ora and can successfully connect to the Oracle RAC using SQL Plus with no issues. I can also successfully ping to the IP addresses with no issues.
I also played around with the JDBC string and added (FAILOVER=ON) but still have same issues.

Please advise.