I just made a clean install of ubuntu 12.04 on my thinkpad and installed sage from 
sage-5.1-linux-64bit-ubuntu_12.04_lts-x86_64-Linux.tar.lzma, and have a problem, apparently with libgfortran (see below).  Any help would be appreciated.
Thanks!
xyzzy> sage
----------------------------------------------------------------------
| Sage Version 5.1, Release Date: 2012-07-09                         |
| Type "notebook()" for the browser-based notebook interface.        |
| Type "help()" for help.                                            |
----------------------------------------------------------------------
sage: plot(x^2,(x,0,1))
---------------------------------------------------------------------------
ImportError                               Traceback (most recent call last)
/home/davidp/<ipython console> in <module>()
/usr/local/sage/local/lib/python2.7/site-packages/IPython/Prompts.pyc in __call__(self, arg)
    550 
    551             # and now call a possibly user-defined print mechanism
--> 552             manipulated_val = self.display(arg)
    553             
    554             # user display hooks can change the variable to be stored in
/usr/local/sage/local/lib/python2.7/site-packages/IPython/Prompts.pyc in _display(self, arg)
    576             return IPython.generics.result_display(arg)
    577         except TryNext:            
--> 578             return self.shell.hooks.result_display(arg)
    579 
    580     # Assign the default display method:
/usr/local/sage/local/lib/python2.7/site-packages/IPython/hooks.pyc in __call__(self, *args, **kw)
    139             #print "prio",prio,"cmd",cmd #dbg
    140             try:
--> 141                 ret = cmd(*args, **kw)
    142                 return ret
    143             except ipapi.TryNext, exc:
/usr/local/sage/local/lib/python2.7/site-packages/sage/misc/displayhook.pyc in result_display(ip_self, obj)
    150     # IPython's default result_display() uses the IPython.genutils.Term.cout stream.
    151     # See also local/lib/python2.6/site-packages/IPython/hooks.py.
--> 152     print_obj(IPython.genutils.Term.cout, obj)
    153 
    154 def displayhook(obj):
/usr/local/sage/local/lib/python2.7/site-packages/sage/misc/displayhook.pyc in print_obj(out_stream, obj)
    142             if _check_tall_list_and_print(out_stream, obj):
    143                 return
--> 144     print >>out_stream, `obj`
    145 
    146 def result_display(ip_self, obj):
/usr/local/sage/local/lib/python2.7/site-packages/sage/structure/sage_object.so in sage.structure.sage_object.SageObject.__repr__ (sage/structure/sage_object.c:1496)()
/usr/local/sage/local/lib/python2.7/site-packages/sage/plot/graphics.pyc in _repr_(self)
    801         """
    802         if SHOW_DEFAULT:
--> 803             self.show()
    804             return ''
    805         else:
/usr/local/sage/local/lib/python2.7/site-packages/sage/misc/decorators.pyc in wrapper(*args, **kwds)
    454             kwds[
self.name + "options"] = suboptions
    455 
--> 456             return func(*args, **kwds)
    457 
    458         #Add the options specified by @options to the signature of the wrapped
/usr/local/sage/local/lib/python2.7/site-packages/sage/plot/graphics.pyc in show(self, **kwds)
   1513         else:
   1514             kwds.setdefault('filename', sage.misc.misc.tmp_filename() + '.png')
-> 1515             self.save(**kwds)
   1516             os.system('%s %s 2>/dev/null 1>/dev/null &'
   1517                       % (sage.misc.viewer.browser(), kwds['filename']))
/usr/local/sage/local/lib/python2.7/site-packages/sage/misc/decorators.pyc in wrapper(*args, **kwds)
    454             kwds[
self.name + "options"] = suboptions
    455 
--> 456             return func(*args, **kwds)
    457 
    458         #Add the options specified by @options to the signature of the wrapped
/usr/local/sage/local/lib/python2.7/site-packages/sage/plot/graphics.pyc in save(self, filename, **kwds)
   2245             SageObject.save(self, filename)
   2246         else:
-> 2247             figure = self.matplotlib(**options)
   2248             # You can output in PNG, PS, EPS, PDF, or SVG format, depending on the file extension.
   2249             # matplotlib looks at the file extension to see what the renderer should be.
/usr/local/sage/local/lib/python2.7/site-packages/sage/plot/graphics.pyc in matplotlib(self, filename, xmin, xmax, ymin, ymax, figsize, figure, sub, axes, axes_labels, fontsize, frame, verify, aspect_ratio, gridlines, gridlinesstyle, vgridlinesstyle, hgridlinesstyle, show_legend, legend_options, axes_pad, ticks_integer, tick_formatter, ticks)
   1720             axes = self.__show_axes
   1721 
-> 1722         from matplotlib.figure import Figure
   1723         from matplotlib import rcParams
   1724         self.fontsize(fontsize)
/usr/local/sage/local/lib/python2.7/site-packages/matplotlib/__init__.py in <module>()
    131 import sys, os, tempfile
    132 
--> 133 from matplotlib.rcsetup import (defaultParams,
    134                                 validate_backend,
    135                                 validate_toolbar,
/usr/local/sage/local/lib/python2.7/site-packages/matplotlib/rcsetup.py in <module>()
     17 import warnings
     18 from matplotlib.fontconfig_pattern import parse_fontconfig_pattern
---> 19 from matplotlib.colors import is_color_like
     20 
     21 #interactive_bk = ['gtk', 'gtkagg', 'gtkcairo', 'fltkagg', 'qtagg', 'qt4agg',
/usr/local/sage/local/lib/python2.7/site-packages/matplotlib/colors.py in <module>()
     50 """
     51 import re
---> 52 import numpy as np
     53 from numpy import ma
     54 import matplotlib.cbook as cbook
/usr/local/sage/local/lib/python2.7/site-packages/numpy/__init__.pyc in <module>()
    134         return loader(*packages, **options)
    135 
--> 136     import add_newdocs
    137     __all__ = ['add_newdocs']
    138 
/usr/local/sage/local/lib/python2.7/site-packages/numpy/add_newdocs.py in <module>()
      7 #       core/fromnumeric.py, core/defmatrix.py up-to-date.
      8 
----> 9 from numpy.lib import add_newdoc
     10 
     11 ###############################################################################
/usr/local/sage/local/lib/python2.7/site-packages/numpy/lib/__init__.py in <module>()
     11 
     12 import scimath as emath
---> 13 from polynomial import *
     14 #import convertcode
     15 from utils import *
/usr/local/sage/local/lib/python2.7/site-packages/numpy/lib/polynomial.py in <module>()
     15 from numpy.lib.function_base import trim_zeros, sort_complex
     16 from numpy.lib.type_check import iscomplex, real, imag
---> 17 from numpy.linalg import eigvals, lstsq
     18 
     19 class RankWarning(UserWarning):
/usr/local/sage/local/lib/python2.7/site-packages/numpy/linalg/__init__.py in <module>()
     46 from info import __doc__
     47 
---> 48 from linalg import *
     49 
     50 from numpy.testing import Tester
/usr/local/sage/local/lib/python2.7/site-packages/numpy/linalg/linalg.py in <module>()
     21         isfinite, size, finfo, absolute, log, exp
     22 from numpy.lib import triu
---> 23 from numpy.linalg import lapack_lite
     24 from numpy.matrixlib.defmatrix import matrix_power
     25 from numpy.compat import asbytes
ImportError: libgfortran.so.3: cannot open shared object file: No such file or directory
sage: