my emac didn't boot correctly?

Tried to install some updates for Java, iTunes. When coming back home got an error message for the installation but didn't pay much attention an shut down the computer. Next day when booting the desktop behaved erratically, with menu bar and folders appearing and disappearing intermitently and not obeying any commands. Tried zapping the pram and the OF Menu but nothing seems to work. Any ideas?
Thanks a lot.
Alberto Cidraes