MacBook 4,1 starts up with 2.6.32.19 but not 2.6.32.20

MacBook4,1 (early 2008 model), Ubuntu Lucid, all updates installed

With the 2.6.32.19 kernel, Ubuntu starts up successfully.

With the 2.6.32.20 kernel (whether in recovery mode or not), Ubuntu switches immediately to a console, which displays a bunch of text and then hangs.

The first time this happened, the last four lines of text shown in the console were: (transcribed from a photo)
------------
0.664507] sd 2:0:0:0: [sda] Attached SCSI disk
0.760094] usb 2-4: new high speed USB device using ehci_hcd and address 2
0.892478] usb 2-4: configuration #1 chosen from 1 choice
1.300089] usb 7-1: new low speed USB device using uhci_hcd and address 2
------------

On the second attempt, the last four lines of text shown in the console were: (again transcribed from a photo)
------------
[ 2.007939] apple 0003:05AC:0229.0002: input,hidraw1: USB HID v1.11 Keyboard [Apple Computer Apple Internal Keyboard / Trackpad] on usb-0000:00:1d.2-2/input0
[ 2.015671] input: Apple Computer Apple Internal Keyboard / Trackpad as /devices/pci0000:00/0000:00:1d.2/usb7/7-2//7-2:1.2/input/input6
[ 2.015794] apple 0003:05AC:0229.0003: input,hidraw2: USB HID v1.11 Device [Apple Computer Apple Internal Keyboard / Trackpad] on usb-0000:00:1d.2-2/input2
[ 2.156539] ieee1394: Host added: ID:BUS[0-00:1823] GUID[001ff3fffe315a4c]
------------

I have not used ubuntu-bug -p linux because that would, presumably, be gathering lots of information from the 2.6.32.19 kernel that works fine, and not from the 2.6.32.20 kernel that doesn't work.

Other problems reported in the past 12 hours with 2.6.32.20 not starting up include bug 561437 (ThinkPad X61), bug 561140 (Acer Aspire, with various other systems piling on in comments), bug 561429 (Acer), and bug 561409. Of these, bug 561140 looks vaguely similar to the first text above, as it contains the text "usb 2-5: configuration #1 chosen from 1 choice".