Java HotSpot Virtual Machine

I have some native code, that in a single thread, loops over a Java method. To improve performance, I tried this:

    static jclass clazz = env->FindClass("foo");
    /*FIXME: GetStaticMethodID crashes with "Bad global or local reference"*/
    jmethodID mid = env->GetStaticMethodID(clazz, "makeEvent", sig);

But with the static declaration of clazz, the JVM crashes on the second iteration. Why? Is this really any different then using a C++ member field ?

My loop is really a bit more complicated then this, in that it starts several calls up. I hate the idea of

A) actually calling FindClass every iteration.

B) passing the clazz pointer through 3 layers of calls, just to avoid calling FindClass

Is there a better way?
Thanks!