I am reluctant to post this because (a) I might have made some dumb mistake in my code, simple as it is, and (b) the problem might be well-known or even hopeless because the cgi module may not be WSGI compliant, but if this isn't going to be fixed then at least the problem should be described in the cgi module documentation.

I run an HTTPServer with a CGIHTTPRequestHandler.
I open an HTML file with a trivial form that simply POSTs an upload of a single file.
I browse, select a file, and click submit.
The web request never completes -- the browser just waits for a response.
Interrupting the server with ^C^C produces a backtrace that indicates it is stuck trying to decode the file contents.

The attached zip file contains:
    cgi-server.py
    cgi-post.html
    cgi-bin/cgi-test.py
    exception.txt
The latter is the backtrace output from when I interrupt the server.

This is on OS X 10.5 with either Python3.1 or Python3.2 from the repository.