LaTeX will give you this error if you have the environment variable TEXINPUTS set incorrectly. In our old LaTeX 2.09 installation it was necessary to set this variable in order to get LaTeX to find all the right files. This is no longer necessary, but LaTeX will continue to honour the variable if it is set, which now results in the system finding all the old (i.e. wrong) files, manifesting first in this error message.
The way to solve this problem is to comment out of your .cshrc and .login files lines where you set any of the following variables: TEXINPUTS, TEXFONTS, MFINPUTS. Once you have done this, log out (including exiting X) and log back in again, and the problem should be gone.
If you have a particularly complex personal LaTeX setup, you may wish to see Where LaTeX Searches For Files for some ideas on how to reorganize your LaTeX directories so that the system will locate your files correctly.