I've got similar problem with geometry shader. I use fglrx module too (ati-drivers-8.501). When I run glxinfo, it shows that the geomatry_shader is not supported (no GL_EXT_GEOMETRY_SHADER4). When I run my code (using glew) it shows that geometry shader is supported but when I use a function of this extension it returns segmentation fault. I'm using Gentoo 2007 x86_64, Radeon HD4850. Thank you.