Read this ticket first!
http://twistedmatrix.com/trac/ticket/4881
Basically, it comes down to running:
mount -t fdescfs null /dev/fd
and putting the equivalent in your /etc/fstab — otherwise, Twisted will have mysterious problems related to file descriptors and child processes. A fix is due for review and should be included in trunk at some point.
Thanks to David (big thanks for hosting), Glyph, JP and Itamar — I had a great time at the Twisted sprint last night 