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Something about distutils/cmd.py breaks inspect.findsource(). I am
unsure if this is a bug with DistUtils or the inspect module.
>>> import inspect, distutils.cmd
>>> inspect.findsource(distutils.cmd.install_misc.get_outputs)
Causes findsource() to receive an IndexError.
From some hacking, I've found that the root cause appears to be that
linecache.getlines() returns a number of lines that do not match the
actual file. (In my case, getlines() returns 405 lines when
distutils/cmd.py has 478 lines.)
This bug causes pydoc to break when it is pointed at distutils.cmd.
This is on Ubuntu Gutsy, Python 2.5.1

I can't reproduce it with 2.5.1 on SuSE 10. Can you please report the
exact traceback you see?

sqlite3/test/types.py also seems to cause the same error, although the
difference is much wider (101 lines vs. 351).

The exact traceback is as follows:
>>> findsource(distutils.cmd.install_misc.get_outputs)
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
 File "/usr/lib/python2.5/inspect.py", line 510, in findsource
 if pat.match(lines[lnum]): break
IndexError: list index out of range

Can't repro either.
I strongly suspect that this is because somehow linecache finds a
different version of the module on sys.path.

Indeed. For the distutils.cmd case, linecache.updatecache() takes
"cmd.py" and tracks that down to /usr/lib/python2.5/cmd.py. This would
also explain the sqlite3.tests.types problem.
The bug seems to be that the inspect module doesn't pass enough context
information to linecache to unambiguously locate the file.

Can you trace this a bit further? Can you suggest a specific
modification that would fix this issue?

When I printed the file name that is being passed to
linecache.getlines() by findsource(), the file name is absolute path.
So there may be nothing wrong with linecache itself. Can you see what
is the name being passed in your case? We still need to trace what
specific setting on OP's system is causing the problem.

depending on the use case, updatecache() will be passed
'distutils/cmd.py', but still turn that into '/usr/lib/python2.5/cmd.py'.
I have not messed with my stock Python modules. My sys.path is:
* /usr/lib/python2.5/site-packages/recaptcha_client-1.0.1-py2.5.egg
* /usr/lib/python25.zip
* /usr/lib/python2.5/lib-dynload
* /usr/lib/python2.5/site-packages/Numeric
* /usr/lib/python2.5/site-packages/PIL
* /usr/lib/python2.5/site-packages/wx-2.8-gtk2-unicode
* /usr/lib/python2.5/site-packages
* /usr/lib/python2.5
* /usr/lib/python2.5/plat-linux2
* /usr/lib/python2.5/lib-tk
* /usr/local/lib/python2.5/site-packages
* /usr/lib/python2.5/site-packages/gst-0.10
* /var/lib/python-support/python2.5/pyinotify
* /var/lib/python-support/python2.5
* /usr/lib/python2.5/site-packages/gtk-2.0
* /var/lib/python-support/python2.5/gtk-2.0
* /usr/lib/site-python
I've also attached the script I used to discover the bug originally.
(Much larger than the snippets I've been pasting here.) Just be warned
that it writes a large number of files and produces considerable output.

The issue is probably related to http://bugs.python.org/issue1665 

Do you happen to be on Ubuntu?
Maybe this is the same as issue #1665 ?

They might be the same bug, with different manifestations.
That bug is starting to get rather annoying.
(At first, I thought it wasn't. Surprise, surprise.)