Memory Error when using Native Method

Hi,
I am calling C++ methods from Java. Everything is working fine except when I make 2 calls simultaneously.
For Example :
I have a native method in Java and it's implementation in C+ by the name MyFunc(int i, String s);
When in the main method I am calling :
MyFunc(1,"A");
MyFunc(2,"B");
I am getting a Memory "Read" error.
Any help on resolving the error would be of great help.
Raj
Sun Certified Java Programmer.

This is really a C question, not a java question.