I'm not sure about why the gfxmode is happening(a quick search on askubuntu only game me ways to fix it not a root cause) but is is unrelated to the missing boot screen.
The "missing" boot screen is normal behavior in 12.04 in my experience, but the link that I provide dates back to Jan 2011.(may have more to do with how fast your processor is, I only noticed this with my new computer, an Intel Sandy Bridge, which I bought to install 12.04 on, my old computer was 6yrs old and alot slower)
paste from The Linux Experience
WHY DOESN'T IT WORK?!
Plymouth is a very young piece of technology and it is still not as
solid as one would desire. One of the most frequent problems is the
one I described above, where you get a black screen with a blinking
cursor instead of your shiny Plymouth splash screen.
Essentially, the root cause of this problem relates to graphics
drivers loading slowly, too slowly for the system to wait for them.
The file system is checked and loaded in a shorter time, thus allowing
X to load, perhaps making it unreasonable to have to wait for those
graphics drivers to load.
If you want to read more about it the link has a goodly bit of information about it. If you just want to get your screen back I will copy the directions form the site(I used these commands myself, I hated looking at the blank screen)
Open a virtual terminal and type the following command:
sudo gedit /etc/initramfs-tools/conf.d/splash
This file may not exist, so you may be creating it from scratch now.
Enter the following content on the file you opened on the previous step:
Close and save the file.
Now, run the following command to commit the change:
sudo update-initramfs -u
After rebooting you will have the splash screen back,also you will be able to see any text when pressing
Esc during the splash screen or remove
quiet splash from the boot commands, without this fix even if you remove quiet splash, you will only see a blank screen until the log in screen(