I am absolutely new to Linux. I just installed Ubuntu 7.10 in my 4 years old Toshiba Satellite P25-S676. The Ubuntu package works beautifully (networking, email, printing, etc.). My surprise came when after a seemingly normal shut down, I tried to restart the computer and it would not boot up; all I saw was an absolute black screen with nothing in it.
I decided to unplugged the computer from the electrical outlet, waited 5 seconds and tried again and this time it restarted without a hitch. It’s a fact that the only way I have to boot up the computer is by unplugging it and plugging it back to an electrical outlet.
Can anybody suggest a solution to this anomaly. Thank you.

Check your powersaver/hibernation settings.

That's where I would start.

I have my laptop on AC power all the time (no battery installed). My Power Management Preferences are: 1) put computer to sleep when inactive for (NEVER), 2) when laptop lid is closed (BLANK SCREEN), 3) put display to sleep when inactive for (6 MINUTES), 4) when the power button is pressed (SHUT DOWN), 5) when the suspend button is pressed (SUSPEND).