When viewing any WebGL demo in MineField the performance quickly degrades
to only 2 FPS. I am using hardware rendering with an NVidia 9800GT card.
If I hide the demo window with another window the FPS improves dramatically.
Any help in improving performance would be appreciated.

Below I have added:
1) output from top when I run with the demo window visible
2) software and system info

Top Output:
-----------

Code :
top - 15:55:46 up 9 days, 13:15,  3 users,  load average: 2.42, 2.40, 1.60
Tasks: 172 total,   3 running, 169 sleeping,   0 stopped,   0 zombie
Cpu(s): 53.7%us,  3.9%sy,  0.0%ni, 41.4%id,  0.0%wa,  0.5%hi,  0.5%si,  0.0%st
Mem:   2074628k total,  2006360k used,    68268k free,   134312k buffers
Swap:  2031608k total,   270952k used,  1760656k free,   272148k cached
 
PID USER       PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND            
 2101  root     20   0  763m 425m  12m R 93.1 21.0 502:31.55 Xorg               
15774 joeUser  20   0  590m 139m  20m R 12.9  6.9  29:08.37 plugin-containe    
15735 joeUser  20   0  827m 440m  59m S  7.9 21.7 200:22.08 firefox-bin        
 2335  joeUser  20   0  159m  70m  13m S  5.0  3.5  99:58.11 nautilus



Software and System Info:
-------------------------

Minefield: nightly build from Aug 23rd 2010

OS: Fedora 9

glxinfo output:

Code :
name of display: :0.0
display: :0  screen: 0
direct rendering: Yes
server glx vendor string: NVIDIA Corporation
server glx version string: 1.4
server glx extensions:
    GLX_EXT_visual_info, GLX_EXT_visual_rating, GLX_SGIX_fbconfig, 
    GLX_SGIX_pbuffer, GLX_SGI_video_sync, GLX_SGI_swap_control, 
    GLX_EXT_texture_from_pixmap, GLX_ARB_multisample, GLX_NV_float_buffer, 
    GLX_ARB_fbconfig_float, GLX_EXT_framebuffer_sRGB
client glx vendor string: NVIDIA Corporation
client glx version string: 1.4
client glx extensions:
    GLX_ARB_get_proc_address, GLX_ARB_multisample, GLX_EXT_visual_info, 
    GLX_EXT_visual_rating, GLX_EXT_import_context, GLX_SGI_video_sync, 
    GLX_NV_swap_group, GLX_NV_video_out, GLX_SGIX_fbconfig, GLX_SGIX_pbuffer, 
    GLX_SGI_swap_control, GLX_NV_float_buffer, GLX_ARB_fbconfig_float, 
    GLX_EXT_fbconfig_packed_float, GLX_EXT_texture_from_pixmap, 
    GLX_EXT_framebuffer_sRGB, GLX_NV_present_video
GLX version: 1.3
GLX extensions:
    GLX_EXT_visual_info, GLX_EXT_visual_rating, GLX_SGIX_fbconfig, 
    GLX_SGIX_pbuffer, GLX_SGI_video_sync, GLX_SGI_swap_control, 
    GLX_EXT_texture_from_pixmap, GLX_ARB_multisample, GLX_NV_float_buffer, 
    GLX_ARB_fbconfig_float, GLX_EXT_framebuffer_sRGB, 
    GLX_ARB_get_proc_address
OpenGL vendor string: NVIDIA Corporation
OpenGL renderer string: unknown board/PCI/SSE2
OpenGL version string: 2.1.2 NVIDIA 173.14.15
OpenGL extensions:
 ...