Toshiba laptop display probs

I just installed Fedora Core 4 on a Toshiba Portege 7140 laptop. All is reasonably well; however, the display has been problematic since installation:

1. When I first boot into text mode my display is legible-functional but small, with a frame of unused screen space around it. It looks like a 640x480 subset of the available full-screen 1024x768, sitting in the center of the screen space.

2. When I issue "startx" from #1 i get a white screen with an "X" cursor (letter "X", not XFree86) in the center.

3. At this point I can use Toshiba's Fn+F5 key combo to cycle through the video modes, which eventually gets me to a fully functional, full-screen XFree86 display.

4. However, when I log out of the GUI (from step #3), things get totally weird. X closes out with a bizarre fadeout to white (a sort of "melting away" effect) and the screen stays white... sometimes. Other times it has reverted to a 640x480 rectangle either filled with ASCII visible white font. Sometimes i can issue commands blindly at this point, to shut down, for instance. Other times the system appeared to be frozen. Cycling through the toshiba display modes doesn't achieve much at this point.

5. If i boot into GUI directly, I just skip #1, and #2-#4 phenomena occur.

Are all of these problems (the small text-mode screen, the GUI "white screen", and loss of revertability to text-mode) redeemable with some type of kernel boot option? (vga=???). (Are they all related?)

Help muchly appreciated!

andrew