Adobe Plug-in issue: JNI_CreateJavaVM call in custom dll hangs

We have a plugin that works in Adobe Acrobat and Adobe Reader. The
plugin is written in VS2008 VC++ and calls into a DLL that we have written.

The DLL in turn uses JNI and calls into some Java code. We've tested the
DLL and calls into Java separately and that works OK.

But when it is called via the plugin in Acrobat it is failing. It seems to die
immediately during the JNI initialization in that ca
se. There is a method called JNI_CreateJavaVM where it hangs.

Do you have any idea why that might happen? Is there something
protected that would not permit a dll within the scope of Acrobat to
call into Java code?