Keyboard selection of address autocomplete in email compose window fails

Not sure if this is a sylpheed bug or a desktop environment bug - as it's only happened since I upgraded to Oneiric.

When I'm not using Google Apps, I use sylpheed as my mail client - I like its low-fi HTML support and the fact it stores mail messages in a maildir-esque structure as separate files.

Anyway, when composing a message in Sylpheed, as one types a message it will try and autocomplete the email address you're typing. In the past, I could use the down arrow to pick one of the alternatives. Now, trying to use the down arrow or tab fails, it just moves on to the next field. I have to grab the mouse to pick.

How do I use the keyboard to select from these pop-up options?

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: sylpheed 3.2.0~beta3-0ubuntu1
ProcVersionSignature: Ubuntu 3.0.0-13.21-generic 3.0.6
Uname: Linux 3.0.0-13-generic x86_64
NonfreeKernelModules: nvidia
ApportVersion: 1.23-0ubuntu4
Architecture: amd64
Date: Sun Nov 6 03:04:34 2011
InstallationMedia: Ubuntu 10.04 "Lucid Lynx" - Release Candidate amd64 (20100419.1)
ProcEnviron:
 PATH=(custom, no user)
 LANG=en_AU.UTF-8
 SHELL=/bin/bash
SourcePackage: sylpheed
UpgradeStatus: Upgraded to oneiric on 2011-10-31 (4 days ago)