Please help - 'Screen' problem at high refresh rates

Dear all,

I am using a CRT monitor to deliver visual stimuli which is connected
to a laptop IBM T43. Since the monitor seems to be a little bit
flickering at low refresh rates, such as 60 or 70Hz, so I want to
increase the refresh rate to 90 or 100 Hz. But the command of Screen
starts to refuse to work after I changer the refresh rate to 80Hz or
higher. Does it mean that the display adapter (ATI MOBILITY RADEON
X300) doesn't support high refresh rate? But why the monitor works
fine when I changed the refresh rate to 100 Hz, just the
command 'Screen' doesn't work? Any idea?

The error I got is (Matlab 7.0):

PTB-INFO: This is the OpenGL-Psychtoolbox version 3.0.8.
Type 'PsychtoolboxVersion' for more detailed version information.
PTB-INFO: Psychtoolbox is licensed to you under terms of the GNU
General Public License (GPL). See file 'License.txt' in the
PTB-INFO: Psychtoolbox root folder for a copy of the GPL license.

OpenGL-Extensions are: GL_ARB_multitexture GL_EXT_texture_env_add
GL_EXT_compiled_vertex_array GL_S3_s3tc GL_ARB_depth_texture
GL_ARB_fragment_program GL_ARB_fragment_program_shadow
GL_ARB_fragment_shader GL_ARB_multisample GL_ARB_occlusion_query
GL_ARB_point_parameters GL_ARB_point_sprite GL_ARB_shader_objects
GL_ARB_shading_language_100 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_ARB_texture_mirrored_repeat
GL_ARB_transpose_matrix GL_ARB_vertex_blend
GL_ARB_vertex_buffer_object GL_ARB_vertex_program
GL_ARB_vertex_shader GL_ARB_window_pos GL_ATI_draw_buffers
GL_ATI_element_array GL_ATI_envmap_bumpmap GL_ATI_fragment_shader
GL_ATI_map_object_buffer GL_ATI_separate_stencil
GL_ATI_texture_env_combine3 GL_ATI_texture_float
GL_ATI_texture_mirror_once GL_ATI_vertex_array_object
GL_ATI_vertex_attrib_array_object GL_ATI_vertex_streams
GL_ATIX_texture_env_combine3 GL_ATIX_texture_env_route
GL_ATIX_vertex_shader_output_point_size GL_EXT_abgr GL_EXT_bgra
GL_EXT_blend_color GL_EXT_blend_func_separate GL_EXT_blend_minmax
GL_EXT_blend_subtract GL_EXT_clip_volume_hint
GL_EXT_draw_range_elements GL_EXT_fog_coord GL_EXT_multi_draw_arrays
GL_EXT_packed_pixels GL_EXT_point_parameters GL_EXT_rescale_normal
GL_EXT_secondary_color GL_EXT_separate_specular_color
GL_EXT_shadow_funcs GL_EXT_stencil_wrap GL_EXT_texgen_reflection
GL_EXT_texture3D GL_EXT_texture_compression_s3tc
GL_EXT_texture_cube_map GL_EXT_texture_edge_clamp
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_EXT_vertex_shader
GL_HP_occlusion_test GL_NV_blend_square GL_NV_occlusion_query
GL_NV_texgen_reflection GL_SGI_color_matrix GL_SGIS_generate_mipmap
GL_SGIS_multitexture GL_SGIS_texture_border_clamp
GL_SGIS_texture_edge_clamp GL_SGIS_texture_lod
GL_SUN_multi_draw_arrays GL_WIN_swap_hint WGL_EXT_extensions_string

PTB-WARNING: Couldn't even collect one single valid flip interval
sample! Sanity range checks failed!
PTB-WARNING: Couldn't even collect one single valid flip interval
sample! Sanity range checks failed!
PTB-WARNING: Couldn't even collect one single valid flip interval
sample! Sanity range checks failed!

PTB-INFO: OpenGL-Renderer is ATI Technologies Inc. :: MOBILITY RADEON
X300 x86/SSE2 :: 2.0.5080 WinXP Release
PTB-Info: VBL startline = 768 , VBL Endline = -1
PTB-Info: Beamposition queries unsupported or defective on this
system. Using basic timestamping as fallback: Timestamps returned by
Screen('Flip') will be less robust and accurate.
PTB-Info: Measured monitor refresh interval from VBLsync = 0.000000
ms [1.#INF00 Hz]. (0 valid samples taken, stddev=10000000.000000 ms.)
PTB-Info: Reported monitor refresh interval from operating system =
11.764706 ms [85.000000 Hz].
PTB-Info: Small deviations between reported values are normal and no
reason to worry.

WARNING: Couldn't compute a reliable estimate of monitor refresh
interval! Trouble with VBL syncing?!?

WARNING: Mismatch between measured monitor refresh interval and
interval reported by operating system.
This indicates massive problems with VBL sync.

WARNING: Measured monitor refresh interval indicates a display
refresh of less than 25 Hz or more than 250 Hz?!?
This indicates massive problems with VBL sync.


One or more internal checks (see Warnings above) indicate that
of Psychtoolbox to the vertical retrace (VBL) is not working on your

This will seriously impair proper stimulus presentation and stimulus
presentation timing!
Please read 'help SyncTrouble' for information about how to solve or
work-around the problem.
You can force Psychtoolbox to continue, despite the severe problems,
by adding the command
Screen('Preference', 'SkipSyncTests',1); at the top of your script,
if you really know what you are doing.


Error in ==> Untitled at 2