[Twisted-Python] twisted-names: Cryptic error with no traceback?

[Paul Marks]

Some users of a program that I'm writing have been reporting this
error that I so far have been unable to track down.  It seems that it
originates from Twisted, but that it skips around my errback handler,
and provides no traceback information:

      Traceback (most recent call last):
      Failure: twisted.names.error.DNSQueryTimeoutError:


My query is made from line 121 here:
http://dtella.svn.sourceforge.net/viewvc/dtella/tags/1.0.2/dtella_dnslookup.py?revision=406&view=markup

Does anyone have any insight as to where this error could be coming
from, and why it isn't getting trapped by my errback function?  I
don't know yet whether this is a problem in Twisted, or if I'm doing
something incorrect in my err_cb.