3 possibilities:
1) If you have the VGAOnly and VGAOnly.info in your Devs:Monitors directory and it might be causing a problem. copy them back to Sys:Storage/Monitors/ and delete them from Devs:Monitors
2) your monitor does not support the saved screenmode
boot without startup-sequence and delete the
screenmode.prefs in SYS:Prefs/Env-Archive/Sys
cd SYS:Prefs/Env-Archive/Sys
delete screenmode.prefs
3) does pressing spacebar in boot menu (hold two mouse buttons) have any strange effects?
Thanks for the suggestions.
I first deleted the screenmode.prefs file as recommended by Daedalus and you in #2 above, but it had no effect.
I then followed your advice in #1. It did have an effect, but not the right one. The upward scrolling still occurs, but it is clearly slower than it was before I moved the VGA stuff out of that directory.
As for #3, hitting the spacebar (or any other key) is just toggling me between the PAL and NTSC modes.
Any other possibilities??? Thanks again.