Frescobaldi 1.20 is in Ubuntu Natty.
Ubuntu Maverick, the version you are using, has Frescobaldi 1.0.2
So what's happening is normal.
Next time check this website:
I don't know if there is a .deb package of 1.2.0 somewhere.
This PPA seems dropped:https://launchpad.net/~frescobaldi/+archive/ppa
I would try to compile it from source.
1) install the dependencies.
The easiest way to get the dependencies is this command:
sudo apt-get build-dep frescobaldi
(hopefully, the dependencies for 1.0.2 are the same for 1.2.0)
cmake must be launched when your working directory is the directory of Frescobaldi sources.
If you use Ubuntu (and therefore Gnome), install this package:
Then you can use the file manager (nautilus) to go to the Frescobaldi sources directory,
right-click and choose Open in terminal.
Then you can try running cmake.
Tutorial you may want to read:https://help.ubuntu.com/community/UsingTheTerminal