Ubuntu 10.04 Panel Slow to Load

I noticed a few days ago that the Gnome Panel takes a long time to show up when I log in. It’s consistently about 25 seconds from the time the background and desktop icons show up until the top and bottom panels show up.
I’ve found a few references to this, but I’m not yet sure what the fix is.
Update: Twirl, an Adobe Air application now takes about 30 seconds to start.

I found some more clues related to IPv6. I vaguely remember a problem with this months (years?) ago on Fedora. The first relates to Firefox and the second is for the OS as a whole. I tried method 3 by adding a new entry to /boot/grub/menu.lst. No joy.

Update 25 July: This morning a raft of updates (163), including kernel 2.6.32-24, were available. After installing them, the panel loads normally again.