CentOS - Sep 2006 - Trouble with X and vnc-4.0-8.1.i386 on Centos 4.4

I have recently migrated from an old, RedHat Linux 9 - based system (Aurox 
9.2) to Centos 4.4.

I am having trouble with vnc causing X unusable until reboot.
By unusable I mean that X screen is either blank or blinking and moving, which 
is not cured by X restart until reboot.

My system is:
Compaq EVO D510 SFF
CPU: Intel(R) Pentium(R) 4 CPU 1.80GHz
RAM: 256 MB
Video: 00:02.0 VGA compatible controller: Intel Corporation
82845G/GL[Brookdale-G]/GE Chipset Integrated Graphics Device (rev 01) (prog-if
00 [VGA])
X: X Window System Version 6.8.2, using KDE in runlevel 3
kernel: Linux version 2.6.9-42.0.2.EL (buildsvn at build-i386) (gcc version
3.4.6 20060404 (Red Hat 3.4.6-3))
Monitor: Dell E176FP (LCD, resolution 1280x1024)
Mouse: Compaq/Logitech PS/2 mouse with wheel

The X driver used is i810

How I get into trouble:

I connect to an NT 4.0 Workstation box running 800x600 resolution with vnc;
my resolution is 1280x1024 so the letters are too small for me and I switch 
resolution to 1024x768 or 800x600 using Ctrl-Alt-+;

When I move mouse pointer so it leaves vnc window (sometimes through bottom vnc
window border, sometimes through right border) then screen starts blinking
with the image displayed multiple times and moving.
Whether the image is moving and how fast depends on mouse position (X
coordinate) on the screen
(the mouse cursor is not visible, btw).

If I move mouse vertically, lower part of the screen is is black.

If I turn on screen saver (which is analog clock) it is displayed perfectly
well on both resolution I tried ( 1280x1024 and 1024x768).
  but when I go back to KDE the screen is again unusable.

If I switch to a text console, text mode is perfectly well, too.

OSD display from the monitor is OK and stable all the time.

If I exit X and then start it again, the screen is either blank while in X, or
blinking.
(if I exit X through Ctrl-Alt-Backspace it was blank;
 if I exit X using KDE menus, and the start it again, it is sometimes blank,
sometimes blinking).

After CentOS is rebooted all is fine.
If I do not change X resolution from the default 1280x1024, vnc work fine all
the time.

I do not see anything special in var/log/messages.

On VT I started X from, I have a message

(1600x1200,Monitor0) mode clock 162MHz exceeds DDC maximum 140MHz

each time I switch from text console to X (or perhaps the other way),
same whether X is working correctly or not.

I have never had that kind of problem with old RHL9-based distribution.

Has anyone seen such behaviour?

I would appreciate any advice. 

(I will send more info is needed, perhaps /var/log/Xorg.0.log ?)

Best regards,

Wojtek

------------------------------

Screen-related sections of my /etc/X11/xorg.conf file are as follows:

Section "Monitor"
        Identifier   "Monitor0"
        VendorName   "Monitor Vendor"
        ModelName    "DELL E176FP"
        DisplaySize  340        270
        HorizSync    31.0 - 80.0
        VertRefresh  56.0 - 75.0
        Option      "dpms"
EndSection

Section "Device"
        Identifier  "Videocard0"
        Driver      "i810"
        VendorName  "Videocard vendor"
        BoardName   "Intel 845"
EndSection

Section "Screen"
        Identifier "Screen0"
        Device     "Videocard0"
        Monitor    "Monitor0"
        DefaultDepth     24
        SubSection "Display"
                Viewport   0 0
                Depth     16
                Modes    "1280x1024"
        EndSubSection
        SubSection "Display"
                Viewport   0 0
                Depth     24
                Modes    "1280x1024" "1024x768"
        EndSubSection
EndSection

Section "DRI"
        Group        0
        Mode         0666
EndSection

On Sep 28, 2006, at 8:46 AM, Wojtek.Pilorz wrote:
> I connect to an NT 4.0 Workstation box running 800x600 resolution  
> with vnc;
> my resolution is 1280x1024 so the letters are too small for me and  
> I switch
> resolution to 1024x768 or 800x600 using Ctrl-Alt-+;
consider using a tool such as gnopernicus (it's part of CentOS).   
it's a general accessibility package, and it includes a screen  
magnifier.  it seems to work just fine on top of vncviewer.

-steve

--
If this were played upon a stage now, I could condemn it as an  
improbable fiction. - Fabian, Twelfth Night, III,v