With 2.6.35-8-generic (from maverick) X detects only one of my two monitors

When booting kernel 2.6.35-8-generic X detects only one of my two monitors (the other goes to sleep with no video signal). Rebooting my computer but selecting 2.6.35-7-generic this time, everything is back to "normal": X detects both my two monitors.

Architecture: AMD64
Graphic card: ATI Technologies Inc RV670PRO [Radeon HD 3850] (using the open-source Xorg driver)
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AcpiTables: Error: command ['gksu', '-D', 'Apport', '--', '/usr/share/apport/dump_acpi_tables.py'] failed with exit code 1:
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.23.
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: michael 1822 F.... pulseaudio
CRDA: Error: [Errno 2] No such file or directory
Card0.Amixer.info:
 Card hw:0 'NVidia'/'HDA NVidia at 0xf4100000 irq 23'
   Mixer name : 'Realtek ALC888'
   Components : 'HDA:10ec0888,1458e601,00100001'
   Controls : 40
   Simple ctrls : 22
Card1.Amixer.info:
 Card hw:1 'HDMI'/'HDA ATI HDMI at 0xf3010000 irq 44'
   Mixer name : 'ATI R6xx HDMI'
   Components : 'HDA:1002aa01,00aa0100,00100000'
   Controls : 4
   Simple ctrls : 1
Card1.Amixer.values:
 Simple mixer control 'IEC958',0
   Capabilities: pswitch pswitch-joined penum
   Playback channels: Mono
   Mono: Playback [off]
DistroRelease: Ubuntu 10.10
IwConfig: Error: [Errno 2] No such file or directory
Lsusb:
 Bus 002 Device 002: ID 04e6:e003 SCM Microsystems, Inc. SPR532 PinPad SmartCard Reader
 Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
 Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
MachineType: Gigabyte Technology Co., Ltd. M56S-S3
Package: linux (not installed)
ProcCmdLine: BOOT_IMAGE=/vmlinuz-2.6.35-9-generic root=/dev/mapper/hostname-root ro quiet splash
ProcEnviron:
 PATH=(custom, no user)
 LANG=en_IE.UTF-8
 SHELL=/bin/bash
ProcVersionSignature: Ubuntu 2.6.35-9.14-generic 2.6.35-rc5
Regression: Yes
RelatedPackageVersions: linux-firmware 1.37
Reproducible: Yes
RfKill: Error: [Errno 2] No such file or directory
Tags: maverick graphics regression-potential needs-upstream-testing
Uname: Linux 2.6.35-9-generic x86_64
UserGroups: adm admin cdrom dialout lpadmin plugdev
dmi.bios.date: 09/26/2007
dmi.bios.vendor: Award Software International, Inc.
dmi.bios.version: F2
dmi.board.name: GA-M56S-S3
dmi.board.vendor: Gigabyte Technology Co., Ltd.
dmi.board.version: x.x
dmi.chassis.type: 3
dmi.chassis.vendor: Gigabyte Technology Co., Ltd.
dmi.modalias: dmi:bvnAwardSoftwareInternational,Inc.:bvrF2:bd09/26/2007:svnGigabyteTechnologyCo.,Ltd.:pnM56S-S3:pvr:rvnGigabyteTechnologyCo.,Ltd.:rnGA-M56S-S3:rvrx.x:cvnGigabyteTechnologyCo.,Ltd.:ct3:cvr:
dmi.product.name: M56S-S3
dmi.sys.vendor: Gigabyte Technology Co., Ltd.