Integration

I want to upgrade iPlanet Web Server 6.0 with JDK/jre 6.0. currently iPlanet Web Server 6.0 is refferring to JDK1.5.0_17 in our lab. I see following error in logs.Any ideas which state is this upgrade is valid or a resolution for the below error would be great.
I tried increasing stack size(StackSize 7168000 in magnus.conf),increasing Sun os filedescriptors and stacksize,jvm.minHeapSize=8388608 and jvm.maxHeapSize=33554432( in jvm12.conf)
Thanks in advance

iPlanet-WebServer-Enterprise/6.0SP6 B06/23/2003 14:40
[18/Dec/2009:09:44:27] info ( 3351): Installing a new configuration
[18/Dec/2009:09:44:27] info ( 3351): [LS ls1] http://stg-bobowww02.attws.com, port 9090 ready to accept requests
[18/Dec/2009:09:44:27] info ( 3351): A new configuration was successfully installed
[18/Dec/2009:09:44:27] config ( 3351): Error occurred during initialization of VM

[18/Dec/2009:09:44:27] config ( 3351): java.lang.StackOverflowError
[18/Dec/2009:09:44:27] config ( 3351):

[18/Dec/2009:09:44:27] config ( 3351): at java.lang.String.hashCode(String.java:1482)

[18/Dec/2009:09:44:27] config ( 3351): at java.util.Hashtable.get(Hashtable.java:334)

[18/Dec/2009:09:44:27] config ( 3351): at java.util.Properties.getProperty(Properties.java:932)

[18/Dec/2009:09:44:27] config ( 3351): at java.lang.System.getProperty(System.java:653)

[18/Dec/2009:09:44:27] config ( 3351): at java.lang.Class$3.run(Class.java:2897)

[18/Dec/2009:09:44:27] config ( 3351): at java.security.AccessController.doPrivileged(Native Method)

[18/Dec/2009:09:44:27] config ( 3351): at java.lang.Class.checkInitted(Class.java:2881)