Just upgraded from 8.04.4 LTS to 10.04.1 LTS, and suddenly my Ubuntu experience has been runined because of this frequent freezes/crashes.

The kern.log says:
Aug 19 23:13:21 ubuntu kernel: [ 2440.380012] [drm:i915_hangcheck_elapsed] *ERROR* Hangcheck timer elapsed... GPU hung
Aug 19 23:13:21 ubuntu kernel: [ 2440.380027] render error detected, EIR: 0x00000000
Aug 19 23:13:21 ubuntu kernel: [ 2440.380044] [drm:i915_do_wait_request] *ERROR* i915_do_wait_request returns -5 (awaiting 214801 at 214797)
Aug 19 23:13:24 ubuntu kernel: [ 2442.824019] [drm:i915_gem_idle] *ERROR* hardware wedged
Aug 19 23:13:31 ubuntu kernel: [ 2450.568583] [drm:i915_gem_entervt_ioctl] *ERROR* Reenabling wedged hardware, good luck
Aug 19 23:13:32 ubuntu kernel: [ 2450.880012] [drm:i915_hangcheck_elapsed] *ERROR* Hangcheck timer elapsed... GPU hung
Aug 19 23:13:32 ubuntu kernel: [ 2450.880023] render error detected, EIR: 0x00000000
Aug 19 23:13:32 ubuntu kernel: [ 2450.880045] [drm:i915_do_wait_request] *ERROR* i915_do_wait_request returns -5 (awaiting 214803 at 214797)
Aug 19 23:13:34 ubuntu kernel: [ 2453.112033] [drm:i915_gem_idle] *ERROR* hardware wedged
Aug 19 23:13:35 ubuntu kernel: [ 2454.217610] [drm:i915_gem_entervt_ioctl] *ERROR* Reenabling wedged hardware, good luck
Aug 19 23:13:35 ubuntu kernel: [ 2454.532015] [drm:i915_hangcheck_elapsed] *ERROR* Hangcheck timer elapsed... GPU hung
Aug 19 23:13:35 ubuntu kernel: [ 2454.532025] render error detected, EIR: 0x00000000
Aug 19 23:13:35 ubuntu kernel: [ 2454.532052] [drm:i915_do_wait_request] *ERROR* i915_do_wait_request returns -5 (awaiting 214805 at 214797)
Aug 19 23:13:37 ubuntu kernel: [ 2456.588020] [drm:i915_gem_idle] *ERROR* hardware wedged
Aug 19 23:13:38 ubuntu kernel: [ 2457.764415] [drm:i915_gem_entervt_ioctl] *ERROR* Reenabling wedged hardware, good luck
Aug 19 23:13:39 ubuntu kernel: [ 2458.080013] [drm:i915_hangcheck_elapsed] *ERROR* Hangcheck timer elapsed... GPU hung
Aug 19 23:13:39 ubuntu kernel: [ 2458.080025] render error detected, EIR: 0x00000000
Aug 19 23:13:39 ubuntu kernel: [ 2458.080048] [drm:i915_do_wait_request] *ERROR* i915_do_wait_request returns -5 (awaiting 214807 at 214797)


And the machine details are:
00:00.0 Host bridge: Intel Corporation 82845G/GL[Brookdale-G]/GE/PE DRAM Controller/Host-Hub Interface (rev 01)
00:02.0 VGA compatible controller: Intel Corporation 82845G/GL[Brookdale-G]/GE Chipset Integrated Graphics Device (rev 01)
00:1d.0 USB Controller: Intel Corporation 82801DB/DBL/DBM (ICH4/ICH4-L/ICH4-M) USB UHCI Controller #1 (rev 01)
00:1d.1 USB Controller: Intel Corporation 82801DB/DBL/DBM (ICH4/ICH4-L/ICH4-M) USB UHCI Controller #2 (rev 01)
00:1d.2 USB Controller: Intel Corporation 82801DB/DBL/DBM (ICH4/ICH4-L/ICH4-M) USB UHCI Controller #3 (rev 01)
00:1d.7 USB Controller: Intel Corporation 82801DB/DBM (ICH4/ICH4-M) USB2 EHCI Controller (rev 01)
00:1e.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev 81)
00:1f.0 ISA bridge: Intel Corporation 82801DB/DBL (ICH4/ICH4-L) LPC Interface Bridge (rev 01)
00:1f.1 IDE interface: Intel Corporation 82801DB (ICH4) IDE Controller (rev 01)
00:1f.3 SMBus: Intel Corporation 82801DB/DBL/DBM (ICH4/ICH4-L/ICH4-M) SMBus Controller (rev 01)
00:1f.5 Multimedia audio controller: Intel Corporation 82801DB/DBL/DBM (ICH4/ICH4-L/ICH4-M) AC'97 Audio Controller (rev 01)
01:00.0 Ethernet controller: Hangzhou Silan Microelectronics Co., Ltd. SC92031 PCI Fast Ethernet Adapter (rev 01)
01:02.0 Modem: PCTel Inc HSP56 MicroModem (rev 04)
01:08.0 Ethernet controller: Intel Corporation 82801DB PRO/100 VE (LOM) Ethernet Controller (rev 81)