Here's a new dimension to the famous What does viagra do.In order to fix the problem,you would have added a vga=791 or lets say vga=xxx to the your /boot/grub/menu.lst.
Recently I discovered that updating your kernel resets your menu.lst to the default settings.You need to edit the automagic kernel settings in order to solve the problem permanently.
Open a terminal window and type the following to edit menu.lst-
sudo gedit /boot/grub/menu.lst or,
sudo nano /boot/grub/menu.lst
Type your password to edit the file.Lets say you had added vga=xxx after reading part 1 of this problem.Now search for a line like this one-
# defoptions=splash quiet
You need to change it to-
# defoptions=splash vga=xxx quiet
This should solve your problem permanently.I'll post a part-3 if I discover any other aspect of this problem.