I think you need call glFlush() after create texture, i.e.:
....
glTexImage3D( GL_TEXTURE_3D, 0, GL_R8UI, 1024, 1024, 1024, 0, GL_RED_INTEGER, GL_UNSIGNED_BYTE, data );
glFlush();
HandleGLError();
ati_meminfo();
....
On windows, please make sure there is ATI_meminfo extension firstly. ATI_meminfo is only available on workstation card. I don't think A8-7600 Kaveri APU is a workstation card.
So you can't use this extension on win7 with your APU.