Projector Video "Swims"

When I use a projector with my RedHat 7.2 notebook,

the projected video wiggles in vertical bands. In the past,
the key combination that toggled the video output, if I
cycled through all possibilities once, would solve the
problem. Now, however, this key combination doesn't appear
to do anything at all. Completely non-functioning. (It's
been months since using the projector: I'm not sure what
may have changed but, for one thing, I'm using a custom-built
kernel instead of the stock RedHat kernel. I changed the CPU
type to Coppermine and enabled ACPI and turned off APM BIOS
[which appears to have had no effect on anything].
     I think the swimming effect might be a refresh-rate
conflict between the LCD and the video projector. Can I
solve that in XF86Config (but what is XF86Config-4 for?)?
Maybe one of the following needs to be changed? Suggestions
would be most welcome.

# [snipped from /etc/X11/XF86Config, nothing like it in XF86Config-4]
# 1024x768 @ 100Hz, 80.21 kHz hsync
Modeline "1024x768"   115.5  1024 1056 1248 1440  768  771  781  802 -HSync -VSync
# 1024x768 @ 60 Hz, 48.4 kHz hsync
Modeline "1024x768"    65    1024 1032 1176 1344   768  771  777  806 -hsync -vsync
# 1024x768 @ 70 Hz, 56.5 kHz hsync
Modeline "1024x768"    75    1024 1048 1184 1328   768  771  777  806 -hsync -vsync
# 1024x768 @ 76 Hz, 62.5 kHz hsync
Modeline "1024x768"    85    1024 1032 1152 1360   768  784  787  823
# 1024x768 @ 85 Hz, 70.24 kHz hsync
Modeline "1024x768"   98.9  1024 1056 1216 1408   768 782 788 822 -HSync -VSync

--
Ed Skinner, ed@flat5.net, http://www.flat5.net/