X.org freezes on startup on Dell Latitude D400 with -21 kernel, but not with -19 kernel

I'm not sure if this is getting filed on the right project, please move it if it is not... I only have one option.

So... just upgraded to Lucid, and with the newest kernel (2.6.32-21-generic), X freezes on startup and hangs the whole machine. X works fine with the slightly older -19 kernel, though. I'm not an X guy, so I have no idea what's going on, though it seems to be failing when it tries to load sil164.so, which it doesn't if I boot the older kernel.

I've attached an Xorg.0.log from the failing startup and an lspci -vv log. If you want further information, let me know. It's an easily reproducible bug. I'm willing to help debug.