[Caelum] ItemIdentityException

Hello wonderful Mogre community. I'm having a bit of trouble with Mogre.

I embedded MOGRE on windows forms. I dispose it like so:
if (mRoot != null)
{
mRoot.Dispose();
mRoot = null;
}
camera.Dispose();
sceneMgr.Dispose();
viewport.Dispose();

if (sceneMgr != null)
sceneMgr = null;

if (OGREWin != null)
{
OGREWin.Dispose();
}

However, when I create a new instance of this after it is disposed, I get this error:

---------------------------
An Ogre exception has occurred!
---------------------------
OGRE EXCEPTION(5:ItemIdentityException): Unable to locate vertex program called Ogre/ShadowExtrudePointLightFinite. in GpuProgramUsage::setProgramName at ..\..\ogre\OgreMain\src\OgreGpuProgramUsage.cpp (line 73)
---------------------------
OK
---------------------------


Any ideas?