java.lang.outOfMemory in oc4j

Hi,
First some background:

I am using oracle oc4j server to host applications in a profution enviroment.
I deploy the apps as EAR files , each of the EAR's is ~5 MB in size.
My server specs are as follows:
2Gb RAM
2x Intel Xeon
Windows 2000 Advanced Server
+ 1Gb of virtual RAM memory.

I have two of oc4j's the servers running.
One has ~20 EAR's deployed , the other instance ~35 EAR's deployed.

Since the number of EAR's deployed grew bigger I started reciving
java.lang.outOfMemory errors on the console window, as well as on
500 java.lang.outOfMemory error on clients connecting via web-browser to the server.

I read some post about this errors and I set the way the oc4j is started with a parameter specifing the increased JVM heap size -Xms 512M and -Xmx1512M.
But this deoas not seem to help. I still get the java.lang.outOfMemory during peak loads when many of the clients conenct. The only thing I can do is a reboot of the oc4j.

Well first think I thought I have to have memory leaks in my code.
But java has a garbage collector that is supposed to do the job for me ( it's not c++)
What is there for me left to do?

I try a new option of starting oc4j from the oc4j j2ee_install manual that thay put overthere:
java -Doracle.j2ee.dont.use.memory.archive=true -jar oc4j.jar
which is supposed to free the memory by not using it for class preloading, but I am more than sceptic about it.

Did any one of you have some problems like that before and has a solution?
Is there some memory leak testing program which I can use to find memory leaks in my application?
Or the only way I can go is by upgrading the number of RAM memory an increasing more the JVM heap size parameters ( but then wont I hit some sort of problems with java 32-bit memory addressing and its abilities to allocate only 1,2GB of memory and not a single byte more?)

any reply will help.
Thanks,
Kuba