This is reported on redhat's bugzilla as well (see url).

Running any GLX application fails with:
r300_mem.c:878: bufmgr_classic_post_submit: Assertion `!batch_bo->pending_count' failed.
Aborted

Here is the output from glxinfo:

[jeremy@localhost dri]$ glxinfo
name of display: :0.0
display: :0  screen: 0
direct rendering: Yes
server glx vendor string: SGI
server glx version string: 1.2
server glx extensions:
    GLX_ARB_multisample, GLX_EXT_import_context, GLX_EXT_texture_from_pixmap, 
    GLX_EXT_visual_info, GLX_EXT_visual_rating, GLX_MESA_copy_sub_buffer, 
    GLX_OML_swap_method, GLX_SGI_swap_control, GLX_SGIS_multisample, 
    GLX_SGIX_fbconfig, GLX_SGIX_visual_select_group
client glx vendor string: SGI
client glx version string: 1.4
client glx extensions:
    GLX_ARB_get_proc_address, GLX_ARB_multisample, GLX_EXT_import_context, 
    GLX_EXT_visual_info, GLX_EXT_visual_rating, GLX_MESA_allocate_memory, 
    GLX_MESA_copy_sub_buffer, GLX_MESA_swap_control, 
    GLX_MESA_swap_frame_usage, GLX_OML_swap_method, GLX_OML_sync_control, 
    GLX_SGI_make_current_read, GLX_SGI_swap_control, GLX_SGI_video_sync, 
    GLX_SGIS_multisample, GLX_SGIX_fbconfig, GLX_SGIX_pbuffer, 
    GLX_SGIX_visual_select_group, GLX_EXT_texture_from_pixmap
GLX version: 1.2
GLX extensions:
    GLX_ARB_get_proc_address, GLX_ARB_multisample, GLX_EXT_import_context, 
    GLX_EXT_visual_info, GLX_EXT_visual_rating, GLX_MESA_swap_control, 
    GLX_MESA_swap_frame_usage, GLX_OML_swap_method, GLX_SGI_swap_control, 
    GLX_SGI_video_sync, GLX_SGIS_multisample, GLX_SGIX_fbconfig, 
    GLX_SGIX_visual_select_group
OpenGL vendor string: DRI R300 Project
OpenGL renderer string: Mesa DRI R300 20060815 AGP 4x PowerPC/Altivec TCL
OpenGL version string: 1.3 Mesa 7.3-devel
OpenGL extensions:
    GL_ARB_depth_texture, GL_ARB_fragment_program, GL_ARB_imaging, 
    GL_ARB_multisample, GL_ARB_multitexture, GL_ARB_point_parameters, 
    GL_ARB_shadow, GL_ARB_shadow_ambient, GL_ARB_texture_border_clamp, 
    GL_ARB_texture_compression, GL_ARB_texture_cube_map, 
    GL_ARB_texture_env_add, GL_ARB_texture_env_combine, 
    GL_ARB_texture_env_crossbar, GL_ARB_texture_env_dot3, 
    GL_MESAX_texture_float, GL_ARB_texture_mirrored_repeat, 
    GL_ARB_texture_rectangle, GL_ARB_transpose_matrix, 
    GL_ARB_vertex_buffer_object, GL_ARB_vertex_program, GL_ARB_window_pos, 
    GL_EXT_abgr, GL_EXT_bgra, GL_EXT_blend_color, 
    GL_EXT_blend_equation_separate, GL_EXT_blend_func_separate, 
    GL_EXT_blend_logic_op, GL_EXT_blend_minmax, GL_EXT_blend_subtract, 
    GL_EXT_clip_volume_hint, GL_EXT_compiled_vertex_array, GL_EXT_convolution, 
    GL_EXT_copy_texture, GL_EXT_draw_range_elements, 
    GL_EXT_gpu_program_parameters, GL_EXT_histogram, GL_EXT_multi_draw_arrays, 
    GL_EXT_packed_pixels, GL_EXT_point_parameters, GL_EXT_polygon_offset, 
    GL_EXT_rescale_normal, GL_EXT_secondary_color, 
    GL_EXT_separate_specular_color, GL_EXT_shadow_funcs, 
    GL_EXT_stencil_two_side, GL_EXT_stencil_wrap, GL_EXT_subtexture, 
    GL_EXT_texture, GL_EXT_texture3D, GL_EXT_texture_edge_clamp, 
    GL_EXT_texture_env_add, GL_EXT_texture_env_combine, 
    GL_EXT_texture_env_dot3, GL_EXT_texture_filter_anisotropic, 
    GL_EXT_texture_lod_bias, GL_EXT_texture_mirror_clamp, 
    GL_EXT_texture_object, GL_EXT_texture_rectangle, GL_EXT_vertex_array, 
    GL_APPLE_packed_pixels, GL_ATI_blend_equation_separate, 
    GL_ATI_texture_env_combine3, GL_ATI_texture_mirror_once, 
    GL_IBM_rasterpos_clip, GL_IBM_texture_mirrored_repeat, 
    GL_INGR_blend_func_separate, GL_MESA_pack_invert, GL_MESA_ycbcr_texture, 
    GL_MESA_window_pos, GL_NV_blend_square, GL_NV_light_max_exponent, 
    GL_NV_texture_rectangle, GL_NV_texgen_reflection, GL_NV_vertex_program, 
    GL_OES_read_format, GL_SGI_color_matrix, GL_SGI_color_table, 
    GL_SGIS_generate_mipmap, GL_SGIS_texture_border_clamp, 
    GL_SGIS_texture_edge_clamp, GL_SGIS_texture_lod, GL_SGIX_depth_texture, 
    GL_SGIX_shadow_ambient, GL_SUN_multi_draw_arrays
glxinfo: r300_mem.c:878: bufmgr_classic_post_submit: Assertion `!batch_bo->pending_count' failed.
Aborted


lspci -v data:
0000:00:10.0 VGA compatible controller: ATI Technologies Inc RV350 [Mobility Radeon 9600 M10] (prog-if 00 [VGA controller])
	Subsystem: ATI Technologies Inc RV350 [Mobility Radeon 9600 M10]
	Flags: bus master, 66MHz, medium devsel, latency 255, IRQ 48
	Memory at b8000000 (32-bit, prefetchable) [size=128M]
	I/O ports at 0400 [size=256]
	Memory at b0000000 (32-bit, non-prefetchable) [size=64K]
	Expansion ROM at f1000000 [size=128K]
	Capabilities: <access denied>
	Kernel driver in use: radeonfb
	Kernel modules: radeon