This was logged to Bugzilla last time but was not fixed.
System is an Asus P5GD1 with MSI 6600 (Nvidia chipset)
and Dell 1920x1200 LCD.
The screen breaks up when the X server starts up.
I have not tried a text install as my office desktop
really does need to run X.
It sounds to me like there may be some confusion here.
"boot: linux text" runs the installer "anaconda" in bog-standard VGA
text mode (640x480), the same mode used by most BIOS. If the BIOS
can drive the display then the text-mode installer can, too.
In this mode anaconda can install X11 and other graphics stuff.
[You might want to try "boot: linux text vga=788" (or even vga=791)
to get more than a 25-line by 80-column display at install time.
This is handy for alternate screens accessed by <Alt>F2, etc.]
The graphical installer uses 800x600 SVGA mode, and the software
used during the install itself may well be different from the pieces
of the final installed system. For instance, the xorg.conf used during
install will be replaced by something else after configuring the
display during firstboot.