Mybe you problems with video is caused because you don't have all codecs needed.
So to have all codec type this in you terminal:

sudo aptitude install ubuntu-restricted-extras libxine-extracodecs
gstreamer0.10-plugins-base gstreamer0.10-plugins-good \
gstreamer0.10-plugins-bad gstreamer0.10-pitfdll

Note: Allways you'll instal or remove you need use the command sudo (super user
do), and type the password.

Now you can see all your videos from youtube.com

to unistall picas type:
sudo dpkg --purge picasa
or try System -> Administration -> Synaptic Package Manager
clic on the bottom search and type picasa.

The rest I can't understande exactly what you want