[mod_python] POST Content-Length bug?

I'm getting a 411 Length Required ("A request of the requested method
POST requires a valid Content-length.") in response to a
XMLHttpRequest, but that error does not seem to report the real
problem; Firebug and Tamper Data clearly show "Content-Length" with
value "30".

I can probably hack the JS to make it use GET instead (which seems to
work), but I figured I'd check whether this is a known bug first.
Could this be 3.1-specific?

Regards,
--Bart Alewijnse